I can't comment on the Mollies (i've never kept any) but I've been keep
neon tetra for quite some time.
My Neons do NOT school all the time. I started with a school of 6 (eventually lost 2 who tried to make a "jump" for it). I have 1 Neon who hangs out by himself pretty much all of the time...he has claimed his stake to a small artificial
driftwood log that I have. He is healthy as could be, looks good, eats well, but just likes to be alone. I was a little concerned at first (thinking he was sick or weak) but its been over a year and he is doing great. He does school with the others when they get scared....