System requirements for multicam 4k video on Fcpx

Either of these will be able to handle it with lots of power to spare. In fact any current mac with enough RAM and fast drives will be able to handle it.

Do get yourself fast drives, that is probably the most important factor.

It won’t help to have a beast of a machine like the Ultra if your media drive can’t serve the media fast enough. Considering the difference between an M2 Max anc an M2 Ultra, you could get some great external SSD (and backup drives) for that. Just a point of view; I hope others chime in on this.

I'd be very surprised if FCP would use more than a fraction of those cores and ram for your use case. The main bottleneck will be reading and writing to and from disc so, as Luis says, you'd be best to prioritise storage - fast external SSDs for editing and maybe a RAID server for archiving. 3 hours of 4x4k will take a minimum of about 500GB. I can edit a couple of 4k channels and several channels of Multicam HD on my humble baseline M1 MacBook Air.

The main thing to ensure best performance when you get your new machine is to take the time to do a clean install and not migrate from a backup. Be cautious when adding any 3rd party apps.

The Ultra unless you need portability. Then you need a MacBook Pro.

My advice is always to buy the highest spec you can afford, even if it means remortgaging your house.

You won't regret it.

Incidentally, what is wrong with your M3 Max MBP?