It has nothing to do with the size of the room, but the limited placement options due to size. Extended low is not inherently bad in a small room, but bad placement is bad in all rooms. A small room forces bad placement. Go subs. The more the merrier.
Actually a small room has inherent challenges because the room dimensions are shorter than the sound waves.
So what happens? Bass builds up unevenly so treatment is required...Treat what you can and then use PEQ (like in ROON) to knock down peaks...
multiple subwoofers are tricky unless you have DSP bass management. Subwoofers don’t help much for problems above 80-100hz...room treatment is best above subwoofer crossover point.
Good news is that a 12x12x12 room CAN sound good. You have front wall and sidewall symmetry. Rooms that have an open sidewall can't really be fixed and IMO have much bigger problems in that they can't create a realistic stereo image.