If you have enough separation between subject and background, and you light subject and background separately, then you can over or under expose the background without affecting your subject.
I have a 4 section backdrop stand that is 12 feet wide, plus a bit for the feet. I usually only use two or three sections depending on where it is set up. Paper and canvas backdrops come in varying widths, and at varying prices. Larger/more permanent studios have two, three, or more, rolls of seamless mounted on the ceiling with chains looped on sprockets to roll them up and down. This saves time and space compared to hand rolling one up, taking everything apart, changing the roll, and unrolling the new colour. A stand is practical if the space is not permanent, and probably less expensive.
I have not tried vinyl backdrops, just paper and painted canvas. If you decide to get painted canvas, photograph it with a flash to see what it looks like. I think they look much better when lit, it really changes their appearance. I would worry about vinyl being too reflective, but perhaps that’s not a problem if they are in general use.
If you want to see the effect of 18% grey before purchasing, find a concrete wall that is unpainted. Experiment with that, it will be close enough.