Miller et. al. also suggest different raise sizes in different situations in Professional No Limit Hold Em based on stack sizes. The more advanced you get, you'll probably want to vary your opening raise sizing for different reasons.
Personally, I don't use the same open raise sizing in all situations - mostly based on my stealing frequency, position, and my read on what Villain's reaction will be to different bet sizes. I very specifically do not vary my raise sizing based on the strength of my hand, I think it's too transparent and exploitable. I generally, though, do use the +1 BB per limper no matter what I'm doing, unless I'm flatting behind someone for a specific reason. But there is no single "correct" set of standards to apply as nevadanick points out above.
For someone just starting to explore this, though, imo sticking to a relatively rigid structure (i.e., use 4xBB +1BB per limper or whatever) is probably a good idea until they get a chance to work through the logic. OP is varying his open raise sizing based on the looseness of the table, which I think is a very good idea.