Yeah it runs Photoshop quite well from what I've heard, I just don't have a subscription so couldn't use it.
I ended up going for the base M3 model as while the extra power of the i5 would have been nice, I was more interested in the fan-less version in the end and thankfully I haven't noticed any slowdown yet.
I did a quick bit of drawing this afternoon in Manga Studio 5 and really liked it. The pen was very responsive and I seemed to be getting all the subtle lines I was trying for. I'm going to try some other software when I get a chance so I can compare a bit more. I tend to use Gimp at work so I'll probably go with that next to see how well the pen responds.