From the blinds I typically only isolate with strong
hands like AT+, A9s, KQ, KJs, 88+ or something like this. But it also depends on the stack depth and the number of limpers. I am a bit conservative here, because its free to see a flop in BB, and cheap to complete from SB. So by making a big raise, we are sometimes just helping the limpers by building a bit pot, when they have position on us.
In position I more or less ignore the limp and just open the range, I would normally open from that position, but I add 1BB for each limper. Sometimes I limp behind with a small pair, and if there are several limpers, I will tighten up. How much depend on stack sizes and the whole situation in general. For instance I am always a bit on alert, if a tight regular suddenly limp, because it could be a trap with AA or KK.