Performance is a question of optimization. Anyone who includes a bolt on RT mod in 3 days or less...I said before that I don't think the xsx BC upgrades would be doing things like shader replacement, out of the box for all games.
But what about taking x enhanced games, since they've already been signed off, should be able to have a simpler time getting signed off again for something like this.
And how much performance does it take to add RT in this fashion?
Bolt-on RT should also be the less performance vs native RT implementations.