drugo

I would say not in a way that makes sense, there may be hacky workarounds like setting nice priorities or messing around with scheduling, but there's no way around hardware limitations. The Pi's CPU, RAM, and IO bandwidth are what they are, and you need overhead to guarantee "snappiness"

What I meant is that overloading the CPU on a Raspberry running pi-hole will make the whole network misbehave and timeout, until DNS requests are able to be serviced again. But since they're not doing that it should be fine :)

It's probably going to be ok to scope them out and experiment a bit, but I doubt you'll get enough performance and stability to run it as production. Paperless' OCR is quite heavy on the CPU - iirc you can disable it but then you lose half of what makes it useful, and Nextcloud also does some processing to files that are uploaded to it. Since you are not running pi-hole or other latency-sensitive services it will probably be fine, it will just get sluggish while it processes uploads.