Same here.
Renoise has terrible performance for me and I have a fairly decent PC (Overclocked Ryzen 5 3600, 16gb RAM, RX6600XT, NVME SSD + 3 sata SSDs, etc) . My projects in Reaper can have 16+ tracks with 8+ plugins each and I barely touch 40% CPU usage… No crackling, no problems. I do masters as a “side hustle” and the plugins are all heavy (oversampled clippers, limiters, calibration plugins, analog modeled EQs, linear phase EQ, etc) and they still work as intended in Reaper, with barely any overloading.
In Renoise, however, it only takes a few plugins (or groups, which make it even worse) to reach 90%+ CPU and start crackling. It’s very annoying. I’m forced to resample everything, otherwise I get the Overload notification everytime I hit play.
I’ve been complaining about this for years… I’ve tried all suggestions, even formatting my PC and doing a fresh reinstall. Nothing works except using a sample based workflow with barely any plugins. Enabling the options to use separate processes for plugins doesn’t help either. Changing multicore usage doesn’t make much difference either (I have 6 cores/12 threads).
Good luck not using resample in Renoise if you’re using modern plugins such as Phaseplant, Vital, Limitless, Neutron, smart:comp, etc.
Alternatively, you can turn off all the mixing plugins while you’re editing (compressors, eqs, etc). Far from ideal (or more like a hassle).
Also, I get the impression that using groups and sends tend to have severe impact on performance. However, turning clippers off is not an option if you’re using a bus structure like I do, because it alters the behavior of some plugins that are on top of the chain (specially compressors).
Omnisphere is actually lightweight for me, it doesn’t serve as a good comparison. Try something newer such as Vital or Phaseplant. Try making a song with 5+ instances of Vital… It’s nearly impossible, even setting Vital to Draft mode under settings (1x oversampling). Even in VST3 it doesn’t do well in Renoise (but it’s perfect in Reaper).
Also, I actually have better performance with VST2 for some plugins (mostly the older ones that have been ported over to VST3).