Are these recommended to be enabled or disabled, and will Nvidia Distance Fog even work if I have an AMD card? As far as I understand it, TruForm is a primitive version of tessellation.

Unless there's some tricks that i don't know about, afaik neither effect will work for AMD users, one is Nvidia only has the name indicates, the other is the old hardware tesselation tech from ATI, that was deprecated a long time ago and is no longer supported in the new AMD GPU's, the new ones only support dx11 based tesselation.

For Nvidia users perhaps the distance fog still works but i don't know has I have a AMD card has well.

p.s - This is what happens when games include proprietary tech or tech exclusive to a type of GPU family, the same has happen with Splinter Cell and its proprietary Nvidia shadow buffers system that afaik not even modern Nvidia users can run, in the other end we have very old games in GOG that have all their original tech still working perfectly today just because they didn't included proprietary stuff.