Effects of unequal RAM and VRAM in rig
I didn't want to hijack this thread. But reading I came up with some questions.

What could it cause when I wouldn't have 1:1 RAM and VRAM? Could it lead to something like CL_OUT_OF_HOST_MEMORY or "just" to some cracking slow down? 

And could you guess what performance loss could it be? And what attack types would be affected the most?

I'm running 8x GTX 1080Ti with 32GBs of RAM. I know I have encountered some CL_OUT_OF_MEMORY while doing HC benchmarks with workloads 3 and 4. I suppose that the RAM:VRAM ratio was the origin of the issue.

Last thing, could please point me to hash types I should use when I want to test the stability of hashcat on my rig? My aim is to be able to run any attack on any hash type without any errors or failure due to RAM or VRAM. 

Not enough RAM leads to CL_OUT_OF_HOST_MEMORY errors. It won't slow down things.

MD5/NTLM should be good candidates for stability testing, although there might be even better ones.