managers are definitely not enough
you shoud have about 2.5 Gb of RAM per core for more effective mining (it's an old information but i don't think that something has changed since)
so for your ryzen you must have 2.5*(8-1)=17.5 Gb of available RAM (or 20 Gb if you will set 8 cores unlike default settings)
if you have less available RAM then divide it on 2.5 and you will get optimal number of cores (but less than 4 doesn't make sense i think)