Some horses don't adjust to them very well, so make sure you have a horse that knows how to take cues from one. I used a hackamore on my gelding and he did not take it well at all. He wouldn't turn or anything and just stopped with the pressure. My mare however listened better, but she can neck rein so it wasn't too difficult. Depends on the horse, really.
I prefer the All-In-One training halter bitless bridle. I have used Dr Cook's and it pinches under the chin and the chin straps don't release so my horse ends up shaking her head. Its like a vice grip from poll to chin. I bought an all-in-one and love it. All my horses have them now and our entire barn too. Missy Wryn makes them and teaches how to train a horse bitless www.MissyWryn.com. Hope this helps
There's many, many bitless options available! Please research as many as you can to find one suitable for your horse, then try a few once you've narrowed it down. Not all horses like the same thing! Some bitless options are sidepulls, indian hackamores, LG zaum bridles, hackamores, bosals, lightriders and crossunder bridles. Feel free to message me if you have questions, though there's lots of information out there to be had already :)
They're pretty strong. I put one on my gelding just to see and it was pretty crazy, he listened but he also became strangely "wiggly" in the body so I had to use a lot more leg. He also hated that the noseband was so tight, with the "cross under the chin" type the tight noseband is essential.
You can ask at a local tack store before you buy what their return policy is if you're worried your horse won't go well in it.
I would check and see how your horse likes it.
I don't use bits, so mine are fine with bitless bridles. The horses I stopped using bits with over 30 years ago didn't mind and actually handled better without a bit, but for them the bit was useless, since they neck reined and never had any pressure on the mouth. I think they just liked not having anything in their mouth anymore.
But we didn't have bitless bridles then (or at least I'd never heard of one back then......no internet). Just made a halter with some rope and attached to long end to the opposite side, or used their halter with reins attached.
Would certanly check how well your horse response and handles without a bit first, if a bit is all it knows. You can train them (that's really what it's all about, since it's the training that controls and not the bit), but it's a good thing to know up front if your horse will handle ok, or would more training be required.