I don't understand. What do you mean by 'true form'? None of the Reflection heritage lineages are, mechanically, under a permanent polymorph or shape change effect. Morph-Risen has a bit of that flavor (and may be another way of playing the game as a dog), but it isn't a polymorph effect.
So their form is their true form. Just like every other character that doesn't have a shape change or polymorph ability.
As long as that's out of illusion / transmutation?
I too don't understand: you aren't under any spell or effect anymore. You ARE what you are so True seeing sees YOU: it doesn't matter HOW you got to be you, but you are what you are. So:
A Clone-Risen shows you as you. A Mirror-Risen shows you as you and a Morph-Risen shows as you. A True Sight only matters is you turn into something other than your normal Reflection self.