I was using a M1 Mac Mini and only 8GB of RAM on it to build iOS apps for maybe a year. It's absolutely doable, though it very noticeably gets a little less snappy when building projects. When building in Xcode and then switching to Firefox to browse for instance, I could tell it took slightly longer to switch tabs and YouTube playback would occasionally stutter if too much was happening.

I also was using an Intel MacBook Pro with 16GB at the time. Doing the same thing there was much smoother and snappier. On the whole, it actually made me want to just the laptop instead since it "felt" nicer. (This isn't measuring build times or anything like that, just snappiness of the OS.)