I had an M1 MBA and it ran my 4k monitor fine. I would use it and the laptop screen at the same time. Great machine. I ended up giving it to my wife and getting

I had an M1 MBA and it ran my 4k monitor fine. I would use it and the laptop screen at the same time. Great machine. I ended up giving it to my wife and getting an M1 MBP because I needed more than 16gb RAM for my workflows.