Hi Craig,
I use LP (Louisiana Pacific) lap siding, it is an OSB material that comes in 8 in wide by 16 foot pieces. It is wood grain finished and primed on one side about 10-11 bucks a piece.
https://lpcorp.com/products/exterior/siding-trim/products/lap-siding Usually found at more independent lumber dealers rather than the Big Box.
I rip it in half and get 32 foot of fascia from each piece. I prime all sides and put on one coat of finish paint (all sides) before installing. Any cut ends during install I coat with TiteBondIII.
Yes I use it for all fascia; curves as well as straight sections. I have taken it down to 6 foot radius but it likes 8 foot or more for ease of install. Had this installed on my old railroad for almost 10 years and the only issue I had was some swelling at the ends of the pieces but no rot or decay.
Hardware cloth support;
No matter how well you brace it the wire cloth will sag from the weight of the soil. In a 2 foot span it can sag an inch or more, you say your using ladder road bed, that’s good so no problem there. Adding more soil to keep the top level just wants to sag the wire more.
I keep my supports no more than 12 inches on center. For instance I build a 3’ by 8’ module; I frame it using 2x4 PT and put in 2x4 cross members on 2’ centers then rip 2x4 in half and use these ripped pieces between the framing members.