Which version of AL works best with P5 ? I read a few threads about AL version updates that work better with P6/P7 as I think the library in P6/P7 is a little different from P5.
I'd suggest to use the latest beta, as there are usually always improvements for any version. P5's library really isn't that different than P6's (other than using Material Collections in the material room, too). And you can just ignore the P7 stuff.