Slow playing preflop seems kind of pointless, just an opinion. If you have a good hand preflop, then I think you should be accordingly. Especially if you're trying to disguise your hand, let's say, just limping in looking for the big blind or maybe the big and small blind to think you're just seeing a flop, not knowing you have a monster, you're just asking for one of them to hit the flop. The chances of them catching something are greater and you're not making them pay for the price of admission.
It depends on the table. If your 1/2 table is full of OMCs who all buy in for the min, there is a big chance that no one but you will ever 3 bet unless they have AA. They call lots of bets, but they rarely raise. If you bet out your typical opening bet, say $8, you might have 5 callers and be in a very tough position post flop. If you bet $20, you might get one caller, just like you want, or you might do nothing but steal the blinds.
So if you're UTG with AA, you limp, because you improve the chance of a 2 bet coming out. UTG+2 raises to $8, there are 3 folds and 4 callers, and then you pop it to $40. Maybe you get one caller, maybe you take the pot. Either way, you're ahead.
On that same table with 6 OMCs and a couple of better, more aggressive players, especially if the stacks are deep, I might open for $5 hoping to get the raise and re-raise before it got to back to me.
On a table with mostly all good, observant players, I would go ahead and open for my typical $7 so as to disguise my premium.