At 10NL 6m my 3bet is 3.7% though it varies by position. Highest is BB then SB then CO, I definitely want to start 3betting more on the BTN and folding more in the SB since I play too many hands there. Though in general I don't think having a low 3bet% is a big leak at 10NL.

When we are IP against people who open fairly wide (say a 32/25 in the CO) but hardly ever fold to a 3bet (discount them 4bet bluffing for now) we should first expand our 3bet value range to include hands like JJ/TT/AQ and value town him.

I think how they play post flop matters a lot in deciding the other hands we 3bet. If they are extremely fit/fold then we can 3bet hands that aren't quite good enough to flat call IP like T7s, 53s, 84s, etc but won't be dominated too often, and cbet most boards knowing that he's going to fold so much of his wide range. OTOH if he's a station post flop (eg flats K8s then calls 3 streets on an K hi board) we should add hands like KQ AJ AT to our 3bet range.

Like recently it's been hammered into my head that playing 3bet pots IP is so good especially vs people that don't adjust (AKA nearly everyone at 10NL), so what I'm trying to do is start 3betting more in position gradually at first and 3betting OOP mainly against people who steal a large % from the BTN but fold to 3bets a ton.