Are they realistic? or should i go bigger?
They are not prototypical. Bigger is more realistic, but takes up a lot of room. In general, cars and locos up to about 65’ are okay for 24". Above 65’ go to 30" curves. The NMRA site www.nmra.org has a page on recommended curves in the Standards and RPs section. Keep in mind that these are minimums for operation not appearance. Also, bigger curves mean less straight track between curves which can make the layout seem smaller.
Enjoy
Paul
Paul is right. The use of easements help getting some of the longer equipment around the curves. I have a section with 24" curve with easement and my 80’ passenger cars go around without derailment. They would look much better with larger curves but I haven’t the room for it.
If you can get a ten foot piece of wood (pine works) and cut off a piece 3/4" by 1/4", you can bend it to create the easement and to give you some idea of what the tightest curve you can live with. If you are using flextrack, you are not bound by rules as to the radius of your curves. You can dtermine what best fits your space and the appearance that you want.
Good Luck
Ken