a Pro-Touring car is basically a vehicle thats been upgraded to modern sports car handling and other vehicle specifications....like the brakes, instrumentation, audio, trim etc etc
a Resto-Mod is more likely to be a little more "old school" in the modifications....may not be as cutting edge in the engineering etc.
My car would be a toss up between being called resto-mod or budget pro-touring....either way would probably be a reasonable description.
Listening to the folks on the Meecum Auto Auction, they were describing resto-modding as the addition of "period correct" aftermarket parts and upgrades while pro-touring was seen as a larger deviation towards technological improvements.
I couldn't substantiate that definition and many seem to use it interchangeably.