You may want to look into getting another RPi 3/4 that would be your harvester and leave just node/farmer/wallet on your current RPi4.
The node is the most demanding part of the code, and when that will get overwhelmed, all other components will be kind of screwed. That also means, that if you don’t need your wallet synced (i.e., you are using a cold wallet), it would be better to not run your wallet at all, as that is another db that potentially interferes with the main node disk r/w access (what may be a problem when node is being overwhelmed).
The RPi4 is powerful enough to do all these functions at the same time. I even plot with the same RPi on top of farming, node, wallet, and harvester, and it works great.