DaVinci Resolve (especially Fusion Comps) slower on M2 Ultra than on M1 Pro?

I am editing my videos in DaVinci Resolve Studio. I do some "simple" motion graphics in the built in Fusion page and bought some plugins for text and backgrounds from motionvfx. Since I got my Mac Studio (Base M2 Ultra, 128GB RAM) i always had the feeling, that it was slower than my "older" Mac which I used before for editing (14" MacBook Pro M1 Pro, 16GB RAM).

Today I put it to an test and the results shoked me... The M2 Ultra took 21min while my (unplugged) M1 Pro took 14min for the exact same timeline...

Then I duplicated the timeline and deleted all motionvfx plugins used in that timeline and all the fusion comps I made. Rendered again and everything went back to "normal". The MacStudio took only 1min while the MacBook Pro took 4,5min.

Exporting and XML to FXP (all effects gone ofc) I experienced about the same. The MacStudio finished while the MacBook Pro was still at 55%.

Not tried Premiere.

When Rendering with DaVinci both machines are using full GPU and nearly all RAM.

When Rendering with FCPX both machines are using about half GPU but nearly the same RAM.

Export was 4096x2048 in H.265

Older tests showed me, that H.265 is way faster than H.264 and since I upload to YouTube H.265 is fine.

Is someone experiencing similar things? Why are the Fusion Comps taking so long? And more important, how can it be, that an M1 Pro with 16GB of RAM is faster than and M2 Ultra with 128GB of RAM?

I hope someone can help me...