#1. The abilities will still work ie. the cards powers would be exchanged. Eg: Svelthlana Vs Jim. S will get Js power and vice versa.
#2. The abilities will cancel each other out.
In my humble opinion, the first option seems most likely.
I just figure opp power works the same way opp damage
ex: phonos 7/2 ->opp dmg if he fight a 1/1 card he will do 2 dmg (not 1) . That i am sure.
so python X Selsya both will have 3 power (selsya will get python power but python will stay with his power since its bigger then the opp)
again, not sure about opp power but i think it works same way then opp damage