My first though was: Why do you call the tracks on the left in the picture for "display-style rails"? It's (a grey version - they were blue back in day) the tracks that were used for 4,5 V trains. My second though was: Why? Those two types of tracks are not meant to be connected and as the RC tracks are smooth while the others are not it will be visible no matter what you do.
If you want to go ahead with it, I think you'll have to experiment a bit. What is possible also depends on what size wheels you want to use, how fast you want our trains to go, and the weight (distribution, I once build a train that could only stay on the tracks when filled with passengers) of the trains you want to run. It's been quite some years since I messed with trains, but as far as I remember the standard wheels are quite forgiving at least when you go slow, and I think the new tracks extend half a stud, so you can eliminate the horizontal gap by placing one of types (I think it will be easier t do under the 4,5 V tracks) on jumpers, but that gives challenges in curves.