Bristlenose Pleco question

I would probably only do one BN in a 40 gallon. I have two (unfortunately both male) in my 60 and they are fine, but they do not "like" each other and each have their own pieces of driftwood.

It depends on whether you want them to breed. A pair or 1m/2f would be fine, 2 males would be crowded, more than 2 females would produce too many eggs for a single male to keep up with.

They are fine solo. They aren't really social, to males will not like each other. the dominant one will chase the other off. It's nothing serious though they are so slow it's like watching 2 really out of shape people try to chase one another. They won't go very fast and they give up after of couple seconds. I have 2 males, wanted a pair one died and was replaced with a male albino as a gift thinking they were the same exact fish. If I did it again I wouldn't have 2 but it's not a issue because of what I said before.