Hey James, thanks for the ideas.
I've been setting everything from the Master computer, the desktop. Setting each time to GPU on both. Previously I'd had the GPU + CPU option on, but I've turned that off so now both are just using GPU.
I've set both to Optix (though I know the 1080 doesn't technically support it) because it processes the BVH much faster. However now the time for render went up from 4 minutes to 10 minutes, compared to the 1 minute on the main desktop solo.
Switching to CUDA didn't seem to help things either, and now the desktop (3080) is actually rendering slower than before.
Neither computer seems to be rendering in parallel still either. So now the laptop is rendering, and then when that's done, the desktop renders. At least according to the render percentages for each computer.
Blender also usually crashes now. Same version, which is 2.90.0 on both. I know it's not a stable release but going back much more means an even slower performance.
I haven't been able to render enough frames now to test if it's any different without CPU, but what might be the cause of the glitching effect? If I can't solve that all of this is pointless to even worry about because I won't be able to use anything that's rendered. (Also, will the files ONLY export as EXR? I'm not a huge fan of the way Blender handles colors in EXR.)
Thanks again. I'm hoping there is a way to figure it out but right now everything seems to just be getting slower hah.