The "distance from speaker to wall" is more important for the larger speakers which can get boomy if too close to the wall. Don't think it matters so much for M2/M3.
Ceiling mounting is probably better from a bass / port "breathing" point of view but may not be so good in any other respect.
Is your room really wide, or is it narrow enough that mounting on the side walls is probably pretty close to where you would put the stands anyways ?
M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8
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