But how do I lower the tension? I think its just the friction in the tube.

It comes with 2 spinning tubes so it does spin freely

Welcome to the world of 3d printing

I will be using PLA

But doesn’t that create an offset weight? My part will probably spin at several thousand RPM.

Some addition to my post: The computer I found is a Fujitsu Esprimo Q957. I’ve read online that they are very power efficient and don’t draw as much. I will probably run some lightweight task almost 24/7 and sometimes heavier tasks for short periods of time. A raspberry pi is for me too expensive for the average specs, even if it is very efficient. I think a upgradable pc or mini pc is best, because they are cheap, but can be easily upgraded without buying a whole new computer.