At 2NL-25NL
My approach would roughly be opening ATC versus nits.
Opening 80%ish vs tight regulars.
Opening 60%ish vs loose(r) players with low 3B
Opening 40%ish vs wide defenders with aggro 3B (or anyone who adjusts to Hero because picking up on high steal game)
Make sure you have your different openranges in your head.
Overfold to 3bets without changing raise first percentage until they showdown specific hands they 3B that pretty much guarantee a high3B% to which you have to adjust.

Random remarks:
There are no REGs at 2NL: this must be an assumption to make. Treating anyone as a reg will hurt your winrate. Don’t expect people To adjust their normal game to you radically, until you see evidence. Then, and only then, adjust. With no info, exploit the general weaknesses you can expect of 2NL players. With info, hyperexploit the playerspecific leaks to the absolute max. Don’t adjust until they show you you have to, certainly not before.

First of all you need to differ the stealing positions CO/BTN/SB

in these positions you can have elastic opening ranges, how much you deviate depends on the sample of hands you have of your opponents and how inelastic they are in their response.

here is a quote of a Top10 6max player in the world about this topic:

“Start to make explo adjustments on BTN/SB/BB villains by your openraise strategy CO (and of course the same for BTN, SB). For example I would explo openraise on the CO 30% vs weak passive players behind and openraise 50% on the BTN. We never want to go overboard with these kind of adjustments and I would never openraise more than 50% on the BTN. We also have to take into account the colliding ranges on the Flop if we explo openraise wider. Which means we will be playing with a wider range on the Flop against a tighter range than average, we already exploited our opponent preflop, so we have to cbet less in this spot to keep our preflop exploit profitable.”