Boy I love it. I built a HO layout back in my HS and college days. It was a LOT smaller than that, slightly larger than a sheet of plywood. But I love it. Haven't had the time or space for one since then.
That is not one man's work. Probably a group or club.
As for the speed of the trains, that is entirely in the hands of the operators (model engineers). Even 50 years ago they had very effective speed controls on the model trains. But there is always someone who wants to see how fast they can go. Duhhh! Back in those days I would sometimes watch the real ones going over the Mississippi on the Huey P. Long Bridge outside of New Orleans. It was a very slow process. Very slow, both up and down.
Make it fit.
You can't win and there is a penalty for trying!