Small form factor builds always end up more expensive than just building in a normal mid-tower. It doesn't help that building a PC right now is just the absolute worst. Memory, SFF power supply, and of course GPU are all over priced right now and nothing is on discount. You're lucky if you spend MSRP. If you find yourself with budget issues due to needing a GPU, you can go to a B550 board and retain almost all of the feature set (and get front panel USB-C in exchange), go for non-RGB memory or get memory that isn't blazing fast B-die, or you can use a gen3 NVME drive since there's little to no difference for gaming. The only other thing is that due to the higher end parts of the rest of your build, spending an additional, and at this point marginal, $100 to go to a 5800x seems like a more "balanced" build and would be more beneficial if you run into the incredibly rare game that loves additional cores or just need more cores while you game.
Cooling in SFF cases is always a challenge. If you're using an AIO, generally you'll intake from the side and rely on passive exhaust. Since you're not pushing your CPU at all, this is OK and you'll also be aiming air at your vrm and memory like a down-draft cooler. If you're worried about exhaust, there is room in the rear to slide a slim 92mm exhaust fan like a Noctua NF-A9x14 by pushing the radiator as far forward as you can. A good chunk of it will be blocked, though.
In the M1, your GPU should be default intaking air from the bottom and passively exhausting from the ventilated sides. There's some radiation from the GPU backplate, but you've got that monster of an M.2 heatsink to protect your drive. Cooling the GPU will always be an issue in SFF cases, so placement of the case itself in your setup is important. Try not to choke the sides or rear to prevent recirculation of warm air. You can remove the bottom dust filter, the bottom aluminum frame, or both, to increase the unimpeded flow of air to the GPU but you'll need to do more maintenance.
My first time building in the Ncase M1 was challening, but incredibly fun. I've reconfigured the internals a few times, for cable management and for swapping out different graphics cards and such, and it's still a rewarding build experience. I honestly want to continue building in smaller and smaller cases, and also see about custom looping in a SFF case. Like, I'm staring at my huge as fuck PS5 and wondering how they're so wasteful with their volume now.