Just want to throw this out there I have a small Union Pacific 0-6-0 steam locomotive and a Santa Fe 1950's war Bonnet is anybody out there mix both Thomas and the Realistic world together in one layout just asking.
I do i have the santa fe that you mentioned and a few real world steam (don't quote me on the names) and then I have most of the thomas line and a few UK locos, two of which are the Flying Scotsmann and the Mallard
I've ran Thomas with a 4 car freight train (the 3 or so days I let him run under his own power) and now he's pushed whenever he makes a rare appearance, he's worked well with knuckle couplers with his own hook n loop coupler.
I removed the gears from the moving eye the make the faces replaceable with magnets so i can take them places and have a adult and child version https://www.flickr.com/photos/86150435@N04/14114416651/ (https://www.flickr.com/photos/86150435@N04/14114416651/)
I run my american steam/diesel locomotives (and one pannier tank) with my Thomas models all the time!
As do I ;D