Typically, it is all or nothing. If they did make it a option to control each one separately, that would be a nice touch, but I don't see it happening.
Well, the quote is "Don't recall who asked, but you can play with the HUD opacity so that you don't see your compass, crosshair,
or bars, if you want."
If he said "and bars" I would read it as all or nothing. That, plus the fact that they give you plenty of options for which markers who you want appear or not appear makes me believe they will be separate. But that is just me. :shrug:
Edit* Either way, that is fine with me though. The crosshair only came in handy for me when it came to moving stuff around in my house. I preferred to use my bow without it.