Hello! I just wanted to confirm that for room-scale, you will need 3 sensors. I can't find recent articles on the matter and wanted to confirm that nothing has changed.
I wouldn't think of it as room scale requiring x amount of sensors - if you have cables long enough you can have room scale with 2 - 1 in each corner.
The problem with only 2 is your hands (the controllers) may be occluded at times. I found tracking to be better with 3 and at the current prices, it's a no brainer, as Kevin Bacon would say.
I find as a general rule if your play space is under 7x7 2 sensor can work just fine. Mount your sensors in opposite corners roughly 7-8ft up point down at the center or your play space. Larger than that may work but I'd grab a 3rd sensor for anything bigger