Hullo and welcome to the forum.
Don't write off R1 curves. They can be brought cheaply and straightened/re-radiused with a cheap rail bender.
I've even used a Black & Decker Workmate to straighten track until I brought a second hand rail bender at a model exhibition near me for a fiver!
Also, look at the real railway, and you will see different types of rail and sleepers/ties used. So mixing and matching is prototypical.
In the UK concrete and steel sleepers have largely replaced wooden ones on main lines.
The narrow gauge Ffestiniog Railway now uses recycled plastic sleepers, just like us railway modellers....
The Ffestiniog Railway has announced that it is replacing the wooden sleepers with brand new plastic ones.
www.railadvent.co.uk