A couple of notes from my experiences. I’ve been using rollers (Elite Arion Mag rollers with 3 level resistance) for a long time (since 2015) and I find I can do all types of sessions on them, including anaerobic/VO2. There is a level of technique to be able to do high watts, in that you pretty much have to sit down no matter how hard you are going.
I use a road bike on the trainer, but the max length will just work for an mtb if it isn’t too long. My hardtail fits, but I doubt a modern full suspension bike would.
Noise wise, if you run an mtb with big off road tyres on rollers, it will be very noisy! The bigger the tread, the louder the noise.