is it best to put your best outside defender at pg and your best inside defender at centre?
To me the best inside defender seems obvious at centre as the best inside scorer on your opponents team will be at centre, but i dont know about the best outside defender.
The only really accurate answer would be: it depends. In general, you want the best outside defender defending the best outside scorer (or if the team doesn't really have outside scoring to speak of, perhaps the best passer instead). The best interior defender probably should guard the best inside scorer. Of course, you have to scout the opposition's roster and games a bit to determine who those might be. And if they vary it somewhat, it might not be easy to line up an individual defensive position outside of playing a box and one.
One thing to keep in mind are that you can play a guy at one position and have him defend as another. It's especially useful if you're training a guy out of his natural position, but it can also be used to try to create an offensive mismatch. And if you're playing against a bot, they'll always have their top salary player at PG, the second at SG, third at SF, fourth at PF and fifth at C, so if you're playing with a roster that's not tremendously better, it's worth checking out the players to see if, for example, he'll be starting a natural center at the point, so you can adjust your defense accordingly.