I've been lusting over https://frame.work/ .. I still don't have one, too broke, but I want it as my next computer.

I hear good things about Lenovo X1 Carbon.

System76 is great too. I had a Bonobo WS that I used for years and it was one of the best computers I've owned.

For your use case, you could probably find something on Newegg in the $600-$800 range that would do everything you need. Granted, I'm a Linux user and I have no idea what kind of computer you need to run Windows.

For multitasking, more RAM is always better. Nowadays I don't run anything less than 32GB. IDK anything about modern processors, but when I'm shopping I always use https://www.cpubenchmark.net/ to compare the processors of computers I'm interested in.