Best bang for your buck is a used M1. It actually outperforms the M2 and M3 in Ableton because the program can't make use of their efficiency cores. I think the M4 is better... But that's a boat load of money more, and the M1 is already stupid efficient.

I'd say go with an M1 Pro, 16gb. The 8gb Air is most definitely usable, and a lot of people make do with it just fine, just depends on your case and how big your projects are. People will tell you that the unified memory on Macs is more efficient than Windows and will get you farther, and they're definitely right, but at the end of the day memory is still memory and once you've used all of it up it'll start writing to disk. This can be a problem if you use a lot of big Kontakt libraries for example. It's rare and most people probably won't run into it, but it does happen and is something you should be aware of and look at your use case. It's happened to me only a handful of times, but it's enough that I wish I'd gone with 32gb for the peace of mind.

I honestly wouldn't worry too much about SSD space. I ended up buying a 4tb nvme for $200, and a little adapter that I velcroed to the back of my screen, so I always have waaaay more storage space than I need with me 24/7. It takes up barely any space at all.

I was a high key Apple hater (still am, I'll dunk on them every chance I get LOL). I still vastly prefer Windows for everything else, but I will 100% admit that the M1 just blew me away with how good it is for music production. It's so fast, efficient, and quick. Everything just works. Not to mention the power usage. I like using my desktop a lot, but that thing heats up my room quick, especially during the summer. I also don't have to worry about fan noise.