Disclaimer: I do not have a high opinion of Johnston. I'd like to think that's for good reason, but it's going to be obvious in the following.
Johnston's plan either involves leaving Atlanta in the hands of the massively understrength militia while the field army maneuvers as he chooses - given the campaign so far, away from engagement with Sherman - or does not exist.
Johnston did not have a concrete plan in place when he took over command of the Army of Tennessee. He outrightly oppose Davis's orders to go on the offensive to retake Tennessee - and was right to do so - and he did not like the position at Dalton because although it was a relatively strong defensive positive it also obscured his vision of the enemy and he could not be sure of whether all their numbers were against him there.
His general plan was to repulse the enemy's attack and counter-attack into Tennessee but without knowing where the enemy was or where he intended to strike this was not possible to plan for at the Dalton line.
Wheeler was singularly unhelpful during this time. Johnston sent him daily orders to scout the gaps and assertain the whereabouts of the enemy armies but Wheeler refused and stayed near Varnell's Station looking for a fight.
As a result Johnston was left blind. Two main placed he thought the Federals would strike were around the north flank of Dalton or at Rome so he placed his 40,000 odd men at Dalton and Polk's 20,000 odd men at Rome. Between them he put James Cantey at Resaca with a reinforces unit or about 5,000 to protect the route between the armies and had to rely on "Red" Jackson and other small, independent cavalry units to watch the gaps between the ridges.
Once driven from Dalton and Resaca he attempted his counter-attack at Cassville, with Hood messing up and him believing in Hood and supporting his decision.
By the time he reaches Atlanta he had to more basic plans in mind. One was to release Forrest against Sherman's supply lines and the other was to use the more compact region to strike at Sherman's columns as they were isolated while maneuvering around Atlanta. Both of these could have complemented each other.
Johnston sees himself as outnumbered by at least two to one (overestimating Sherman's forces greatly and probably underestimating his own - in reality, he has an army about 62% of Sherman's), has never shown any great inclination to press an attack* except maybe Seven Pines (which is hardly an inspiring performance by any of the senior generals in gray, though that reflects on more than just Johnston, it's not reassuring), and has no great interest in - or at least has shown nothing that would justify believing he has any great interest in - holding Atlanta. And to do so defensively would require tying his army down to a siege.
Doing so offensively would require a far more aggressive mentality on his part and cooperative subordinates. The first can be made a POD. The second would take an earlier POD.
An agressive mentality alone would not have been enough to hold Atlanta with an offensive-defensive strategy - Hood proved that - there needed to be the balance between agression and realism. Johnston had that in 1861 - and, as an asside, 1st Manassas was another battle where Johnston showed a desire to press the attack - but after his wounding it seems to have gone askew.
[quoe]Also, even if Johnston is aggressive, and even if his army does work as a team, how does he beat Sherman? Sherman has a larger army, very good subordinates that do work together (including Thomas, one of the best generals of the war), and the advantage that its hard to dislodge a large ACW army. Raiding Sherman's supply lines . . . Johnston has refused to send Wheeler to do it (and Wheeler doing so is a joke anyway), and Forrest's men are too far away/need to be elsewhere. So that possibility is out unless things change.[/quote]
Forrest would not have been too far away if he had not gotren distracted after Brices Crossroads. His great victory left Georgia open to him and would have allowed him to operate behind the Federals before Sherman had even gotten past Dallas. Instead of pressing on into Georgia, Forrest chose to head back into Mississippi.
Wheeler, as you said, would have been a joke. Wheeler hadn't been supportive of Johnston from the very beginning of the campaign and would prove later that he was not capable of commanding a unit more that a day's ride from a higher HQ. Beauregard had to beg Davis to get rid of him and only got Wade Hampton and Davis didn't want Hampton to be in South Carolina anymore.
Frankly, the only thing wrong with Retreatin' Joe being replaced is that Davis waited too long to do it, instead of recognizing that Johnston was not the man who could or would (I don't know which, so let's be generous for the sake of my - British? - friendly opponent in all Johnston based discussions) succeed here.
* Bentonville is in 1865, so I stand by "hasn't shown any great inclination" as of this point.
Which would be fair if Davis had someone better to replace him with. He didn't. Lee was never going to move out of Virginia, Longstreet was deemed irreplacable to Lee and had been unimpressive in the few independent commands he'd had anyway, Hardee was steady and reliable but had turned down command of the army and hadn't shown any great independent thought, Hood was no where near ready for the role when he got it and Beauregard didn't have a realistic enough approach to even keep Sherman at bay - he was completely confuse by Sherman' maneuvers during the March to the Sea and the Carolina's Campaign.
For better or worse, Johnston was the best man available and none of the possible replacement would have faired any better.
P.S. Nytram will probably stand up for Joe, but I do think he and I agree this is a heck of a problematic position to try accomplishing something in, and Johnston rightfully or wrongfully feels Davis is out to get him - not a good basis for establishing something between him and Davis whoever is to blame, which for discussion's sake should be left out - the point is, their relationship sucked, Johnston's message on his intentions just prior to this is at best terse and at worst . . . let's just say that their relationship sucked.
The problem with the Johnston/Davis relationship during this time is that there was no impartial go-between. Johnston and Davis hated each other. Johnston thought Davis was setting him up to fail and Davis thought Johnston was working with his political opposition to undermine him.
What they needed was a Robert E. Lee inbetween them. Someone who was friends with both, who wouldn't be drawn into the bickering, who wouldn't pick sides. What they got was Bragg.
Bragg was a bitter vendetta machine driven by the sole purpose of sticking the knife into those who had slighted him and for some reason he took Johnston's critical annalyses of the AoT's ability as a slight and spent the rest of the campaign undermining him. This added to Hood and Wheeler and even Hardee's corrispondence behind Johnston's back made the job exceedingly difficult for Joe. Hardee, at least, followed orders without question but Hood and Wheeler both refused to do what Johnston ordered them to - Wheeler refused to scout and Hood refused to attack at Cassville.
A result of Bragg's lack of impartiality meant that Johnston was getting all these unreasonable demand from Richmond - such as; immediately attack into Tennessee or send half your army to Richmond - while anything he asked for was refuse - such as reinforcement or Forrest to be sent into Georgia. This left Johnston feeling put upon, left him feeling isolated and unsupported so his corrispondence with Richmond became even more clipped and terse.
Additionally, Johnston didn't trust Davis with sensitive information - this being a result of the Richmond newspapers tending to publish his plans a day after he'd told Davis them in 1861 - so he was not prepared to send them to Richmond or trust them to Davis.
If John C. Breckenridge had been Secretary of War during this period the Johnston/Davis relationship might have been manageable and the Confederates may have pulled together for the good of the cause instead of quarrelling with each other.