I have a M1 MacBook Air 13" and spec wise there is no issue in my FCP setup. I think the newer chips will be amazing on both 14 and 16". Having said that, I still prefer my older 2018 15" MacBook Pro due to the size. I find the bigger chassis of the 15" allows my hands to fit more comfortably beside the trackpad. It's a more relaxed fit ergonomically. Also, the bigger display is also appreciated. That's why I've been holding out for the 27" iMac refresh. It does make some difference with FCP, but especially with Lightroom where you have lot of things present.
Also, I'm not sure what kind of projects (size) you will be doing and what your workflow and portability requirements are, but you may want to consider larger storage options as well.
I use an external SSD for editing with FCP whenever I'm doing any large projects. However, when I'm doing small projects, I'll sometimes just do them straight off the internal. It's so nice being able to move the laptop around without worrying about the SSD and dongle hanging off.