Reducing the number of outputs was your advice I followed, which is working much better now. The way I grouped it was the only solution that was plausible for me.
Your proposal 1 would be to load all sample libraries on 1), the slower PC (if I understood that correctly). And your second proposal would be to load all sample libraries on 2), the fastest PC. I can see how this would work and better performance (especially proposal 2 which has less network send, being only midi). But for me there are two drawbacks: a) Your proposals are both solutions for loading only one PC with sample libraries, and b) both would have Cubase run on the slower PC, the one I only connect to via Remote Desktop.
a) I thought I had posted this as well, but reading back it
might have slipped me. What's important to me is that I can utilise as
much RAM as possible, thus using RAM of both PCs to their fullest
extent (I'm already purging quite a few instruments). So I have to split my sample libraries, meaning (as far as I know) I will need VEP on both PCs and I will have to use many outputs with audio input plugins.
b) Running Cubase via Remote Desktop is sluggish and I'd have to fix my soundcard, speakers and midi controller to that PC as well.
The way I've currently set things everything's working alright. I 'benchmarked' my MIR yesterday and the grouping doesn't seem to be that bad, because I could never have used so many ungrouped outputs in there, not by a long shot. MIR is amazing, but hungry.