>>20835053No surefire way to tell since they can build it to screw with your assumptions without destroying synergy.
For example, the forces of nature set-up which includes a Pursuit trapper + defogger/rapid spinner+ a way to handle chansey would usually be Y but then you realize that Tyranitar (pursuit trapper or not) and Keldeo are good pokemon by themselves and having hazard control is mandatory if you're using Zard.
If it's a sun team, you can think it's Y but X actually does good work in a sun team with just Ninetales providing the sun. Safe to assume stall teams are usually bulky wisp X though since Mawille got banned.