A nice discussion. I am still thinking about a small layout this summer. My study seems like the track and bending and other things are a lot harder to learn than just deciding on a loco! That looks like the easy part.
Someday... Hopefully while the company is still around, I plan to go with dual-gauge from Sunset Valley Railroad. All my old toy locos, Mamods, and Millie are O-gauge, but my Ruby is 45mm
https://www.sunsetvalleyrailroad.com/track---rail.html