Using the shared evo stone to grab all 3 legendaries and deciding later which to evolve, will PG change the runes out if the dragon I’ve chosen isn’t the one I initially went down?
If you “ascend” it to mythic you can get the two runes and the glyph that you would normally get in the dragon’s line through its mythic branch (without using any ascension tokens). These are in addition to the two exotics that you can get using ascension tokens.
The mythic line has the same set of runes so you will get them no matter what unless you for some reason pick the wrong mythic Ascension stone to unlock. If you get both the leg and mythic of the same dragon then you end up with 2 sets of the same 3 runes (unfortunately we cant use them both on the same dragon)
You can take both the sorcerer branches to get two sets of hp based runes and glyphs which seems to be a rarer type.