I have an M1 Air 8GB and a 2018 MBP 16GB. Performance feels about the same until the Air hits swap, then the old Intel MBP still outperforms the M1 Air.
My 2018 MBP 15 is the i7 model, while it gets warm it never had the overheating issues the i9 models had. I also had the battery replaced under AppleCare about 10 months ago so it still gets 7-9 hours of battery life.