Bristleworms are considered part of your clean up crew getting to those hard to reach places snails/hermits can't get to. Some folks don't like them just because they are ugly, but are still beneficial.
Short answer: Ugly, but good. If you spotted two more, then more than likely there are way more than you think.
Are you asking if that's a bristleworm or if bristles are okay? If later I agree with @brmreefer. They'll typically come out in lower light especially if you've just fed.
I'm still trying to figure out the distinction between small bristles and fireworms. I can tell the difference when they are big ;Blackeye lol
Don't know, but I have heard that if you touch the bristles then you would start getting a itchy and irritated sensation similar to touching fiberglass. Have not wanted to test that though... ;Happy