[MacDoc]

Correctly for a triple channel machine use 3 or it drops to dual channel but it's very minor gain.

Processor upgrades are inexpensive for that model.

 

[MacDoc]

If it is doing what you want then you don't really need a processor upgrade.
Any processor trays up to 3.33 12 core will slide right in but you have to consider that any M1 will run circles around it.