Ive experimented with this over the years and have found what im sure you already know now.
Putting the guitar sim in each separate track as Jonsey mentioned is the best rock to throw here.
Put 1 sim in each track then pan them hard left and hard right / send them both to your guitar Bus.
I typically send all distorted guitars to one Bus and all semi clean to another bus.
You can get away with EQ the buses to get a independent sound (I use Softube's Grand Summit EQ/Compressor)
But even then I find its not as powerful as if I put it in each track separately.
Only using delay, Reverbs, Chorus FX for buses to be feed by a send or sometimes using it on an instrument Bus to feed a small group of tracks.
there are no rules of course but I wouldn't be worried about saving resources (if that's why you are trying to share a sim by using it on a bus) Most Sims are not to CPU heavy).