Well, the most obvious consequence may be that Gemini and Apollo could very well land on ground and not water. Gemini land landings were scrapped because of
the paraglider fiasco; as for Apollo, early on (think it was in 1962 or 63) it was decided it would land on water.
Land landing of both capsules has some props and cons
Pros
The crew is easier to recover, and the capsule (eventually) can be reused since it is not ruined by saltwater.
Cons
Land landing systems are slightly heavier since the ground is harder than water. Cushions or retrorockets are heavier.
And of course when retrorockets don't work, you end with a Komarov.
Grissom death by drowning may not change Apollo 1 - since it was a whole different issue (pure oxygen fire).
If Gemini was forced to land on land and not water, it could have serious consequence on the paraglider story (we have to make this thing work, no way Gemini lands on water). The issue is that the paraglider just can't work - its not a classic parachute made of cloth but a rigid structure of steel tubes to be deployed in flight, and that's a bad idea.
The OTL paraglider fiasco was already bad, impacting Gemini severely. Now if NASA heavily insisted in making that thing work, things could go pretty bad. Then, delays with Gemini may delay Apollo...