If they bother you (they bother me cause I have a bad reaction to stings) the best way I’ve found is using a syringe around where they are. Mine hide in my large zoa garden so I irritate the zoas and suck those bad boys out. They’re quick so you gotta be quicker!! Use a turkey baster for the big nasty momma ones. Good times to hunt the big ones are at night, when they’re crawling around for food. After you’ve removed all you can try feeding the tank less. If they don’t have enough food then they can’t reproduce. I doubt you’ll eradicate them, but you’ll have significantly less this way. Good luck!
No they are good to have in as they get into small tiny holes your snails can't even get to and clean them out. They don't eat coral, and will only go after dead/dying fish.
Some find them unpleasant as they are a worm and they don't want them in your tank.
There are types that are not good though, but the common bristle worm is nothing to be bothered about and is free CUC and a really good one at that.
"In the wild, as well as your tank, these worms are incredible cleaners. They are scavengers and will eat any dead or rotting thing in your tank. This includes leftover food and dead animals.
They are also able to move through rocks and crevices and get into places other organisms cannot. They make great additions to your tanks cleaning crew.
Any organism that helps you clean the tank without causing your tank problems is a bonus.
Because these organisms enter the tank typically in live rock, it’s likely you will not have to pay for these little cleaners.
The good species can be just as effective at cleaning as snails or even some starfish."
" Bristleworms may look ugly and a little creepy, but most are actually good for your tank—if they are not the poisonous type. They consume materials in your tank that would otherwise decompose and produce ammonia, adding to the load that must be processed by your biological filter. Bristleworms primarily are scavengers and consume uneaten food, detritus, and carrion in a saltwater aquarium. "
I agree with @Fishurama but I personally hate the really big ones (I mean like 6” or bigger) a small conch shell baited with a tiny piece of catfish stink bait every couple of months usually does the trick, you gotta sit there and watch it though.