The versatility helps, but Paige's versatility is even more important in that regard. If Geno wants to put in a PG for a SF or visa versa it usually isn't a problem. For example if Caroline, Q, or say Morgan was at the 3, then KK or Chen could replace them if needed. The reason is if Caroline or someone else who more a natural 3, is in the game then Paige is probably playing the 1. Bring in a 1 and take out a 3, no problem because Paige just moves to the 3.I don't see Chen starting instead of KK. Off the bench she can sub for Paige, Shade or KK.
Basically as long as Paige remains in the game you can substitute any perimeter player for any other perimeter player even if their skill-set and best natural position is quite different. Paige is our best player at 1-3, and except for Sarah maybe at the 4 as well. Now when Paige is sitting (not often) the versatility of Chen and other outside players becomes more important.
Geno had a situation where his hands were largely tied last year as far as strategic or situational substitutions were concerned. He had to go with what he had, and substitutions were made more based on needed rest than game strategy. This year he can much more of a game coach, because he has great versatility, mostly because of Paige, and a much deeper bench.