Been shooting my .300WM for a long, long time without a brake. Never felt the need for one. I'll take a little recoil over that horrific noise any day. My son started shooting mine when he was 12-13 years old, and never had issues. He killed deer and several hogs with it.In my opinion a .300 win mag needs a brake.
Personal preference I would go with a brake that can be turned on or off.
There are several on the market that operate very similar to the Savage factory brake that came installed on some of their rifles with the "AK" designation in the model number. I love this this feature and find it quite handy and be it on or off it doesn't seem to change point of impact at all. It does however do wonders to mitigate the recoil and adjust direction of muzzle blast and noise level. The ones I'm familiar with are sleeved with a detent ball allowing the ports to be opened or closed with a simple twist of the sleeve. They do have to be kept lubricated before storage.
It looks like "Brockman" and "CP convertible" are a couple that pop up with a quick google search.
Good luck.
P.S. 5/8"x24TPI is pretty much adopted as a widely available standard thread. There are plenty of other muzzle brakes and thread patterns available so having your barrel threaded to match a quality brake shouldn't be a problem.