Depends on what course I am going to play. For fast greens, I will typically put on vinyl plank flooring. For regular greens, upstairs hallway on the carpet.
I used to have one of those 'competitor' mats, but it just caused me to get my stroke off centered to play the break in the mat.
I'd like to test the medium speed as that is what speed my home course is set at most of the time.