Open raising is a balance between not giving the BB a good price to defend and realize his
equity, and not losing to much, when someone behind put in a 3-bet. So in tough aggressive games, where people mostly fold or 3-bet, a relatively small size like 2,5 BB work well.
The mini-raise is typically giving BB to good a price to fold, but in the late stage of tournaments, where stacks are very short, it can work, because BB cant really afford to invest anything in getting involved in some marginal spot out of position with a junky hand.
In softer games, including the early stages of tournaments, 3BB is still a good standard open size to use, and sometimes you can even go larger than that, if people are really calling stations, and there is very little 3-betting going on.
In online games I would not advocate staggered bet sizing like going larger with your very big hands. I think, in todays games, bet sizes larger than 3,5BB really stick out, and most players understand, what they mean, and dont make many mistakes against them.
But if there is an absolut goofball at the table, and especially at very low stakes like 2NL, you could still experiment with it. If he is going to call 5BB just as much as 3BB, then why not go to 5BB, when you have aces or kings and want to build a big pot.