When you say lag spikes what kind of thing are you talking about? I have an M1 iMac I run pretty’s hard and I’m not sure what kind of behaviour you’re seeing.
Anything weird showing in Activity Monitor or Console?
If it refers to random beach balls for 30 seconds when accessing disk ether directly or through apps... yeah I get that. I found it disappointing, a flaw in an otherwise great machine (M1 Mac mini).
I have 16BG too. I have a Time Machine backup set up for a disk plugged into an AirPort Extreme, could that be the issue? (The machine connected to the network using WiFi if that matters.)