Can you use the new models as either ship? Meaning can the new X-Wing be used with a T-70 maneuver dial and a regular x-wing dial?
Question about the new core set.
No.
The book does say no.
In casual play though I doubt anyone would mind.
I certainly plan to use the FO TIE models as regular Fighters for a while, until I am more comfortable with the new stuff.
No.
Right. For official purposes, the T-70 X-wing is a T-70, and the TIE/FO is a TIE/FO.
FFG isn't going to send stormtroopers to your house and force you to do it that way at blaster-point, of course. But if you're at a tournament, you'll need an original X-wing to represent Luke Skywalker and a neXt-wing to represent Poe Dameron.