I used FCP on an M1 Air with _8gb_ to edit 4K videos for over a year. Assuming you have enough fast storage (or are happy to use a proxy workflow), it certainly can be done, although everyone’s workflow is different. Assuming no storage speed bottleneck, timeline scrubbing was smooth up to about 2x forward or backward, from memory - after that you hit decoder limits. Proxy workflow gets around that too, though. Render times on even the M1 were a big jump over Intel chips. If Apple has a 2-week return policy where you are, why not give a 16gb M2 Air a try and see if it meets your particular needs?