What if the DNVP, and not the NSDAP, got traction in the late 1920s and took over Germany in the early 1930s? Would they pursue war like the Nazis? Would their war aims be more plausible?
"Took over"? The DNVP had 20.5% of the vote in 1924, but declined to 14.2% in 1928 and 7.0% in 1930. Through 1928, their platform included restoring the monarchy.
Let's say that the DNVP "takes" off in 1928-1930 - because, perhaps, the Nazis don't (Hitler dies of cancer or something).
OTL, in 1930 the NSDAP got 18.3%. We'll give most of that to the DNVP, which draws 19%, with a rump Nazi party led by the Strassers and Goebbels geting 6%. Other parties as OTL. That leaves the seats in the Reichstag as follows:
DVP ------ 30
BVP ------ 19
DBP ------- 6
KPD ------ 77
NSDAP ---- 37
DNVP ---- 111
SDP ----- 143
RPDM ----- 23
CNBLVP --- 26
Zentrum -- 68
CSVD ----- 14
VRP ------- 3
DSP ------ 20
Total --- 577
The DNVP would be in a strong position to form a coalition government. But the KPD, SPD, and Zentrum would have between them 288 seats, leaving 289 for the DNVP-led coalition, unless the DNVP could ally with Zentrum. The Zentrum would not join if the NSDAP was included, though. Also, under Goebbels and the Strassers, the NSDAP would be socialist and opposed by DVNP leader Hugenberg. (They hated him in return.)
Thatl leaves 320 seats for the DNVP coalition, so it could omit one or more of the minor parties.
Thus it is probable the DNVP takes power in 1930. This is a poisoned chalice, as it is unlikely the coalition can do anything to prevent the slide into depression.
But let us guess that Hugenberg consolidates most of the lesser parties under the DNVP label, and that the KPD/SPD split keeps the left out of power. The Nazis cause more violent trouble, and Hugenberg uses this as an excuse to suppress the NSDAP and KPD. The DVNP has the Stahlhelm veterans' militia as its strongarm squad.
By 1932, there are only four parties left
DVP ------ 50 seats
DNVP ---- 242
Zentrum -- 82
SDP ----- 203
Total --- 577
Hugenberg, much as Hitler did, extorts an "Enabling Act" from the Reichstag with the threat of violent takeover with Stahlhelm force, buying the agreement of the DVP and Zentrum with promises of moderation.
What would the Hugenberg regime do? Repudiate Versailles and begin German rearmament. It would however be on a much smaller scale than Hitler. There would be nationalist agitation, and a demand for the return of lands lost in WW I, and even of Germany's colonies.
Assuming Hugenberg stayed in power - he would abrogate the office of President when Hindenburg died, and probably adopt the title of Fuhrer. It should be noted that OTL, Hugenburg was included in the first Nazi cabinet, but was removed in part to his opposition to job-creating public works programs supported by all the other ministers. So it isn't clear that he could stay in power, as he wouldn't be doing much to remedy the crisis.
Hugenburg would be somewhat aggressive in foreign policy, but less than Hitler. He would not dare to "saber-rattle" as much, and almost certainly would not initiate any war involving another Great Power. He would be what has been called "Wilhelmine imperialist"'; seeking a Great Power role for Germany, and domination of eastern Europe, but not control of the world or any other messianic ambitions.
Opposed by France, Britain, Italy, and in some ways the USSR, Germany would remain mainly quiescent. I could see the annexation of Austria. I don't think he would threaten war to get the Sudetenland.