I agree, not a fan of the adjustable objective and capped turrets on the BR.
I have two NF NXS 8-32x56 scopes with the NP-R1 "hashmark" reticle, three NXS 12-42x56 scopes with the NP-2DD "dot" reticle, and one Competition scope with the CTR-2 "fine crosshair + dot" reticle. All have been used on F-TR rifles. All of the NXS scopes are still being used regularly on my competiton rifles, if that tells you anything. I removed the Comp scope because the reticle is simply too fine for my eyes to see any longer, which is kind of a deal-breaker. The NXS scopes all have 1/8th MOA turrets and are excellent choices (IMO) for F-TR competition shooting. I do not feel like I've ever been "held back" by one of the NXS scopes.
I also owned one of the 12-42x56 BR scopes. For me, the front/objective parallax was a complete deal-breaker. I could not reach around with my "T-Rex" arms far enough to change the parallax setting without crawling out from behind the rifle. I found it completely maddening. I had mounted that particular scope on a .22 rimfire rifle with a "0" MOA scope rail. It would just barely zero at 100 yd with typical Eley/Lapua match ammunition. As you noted, a 20 MOA, or even 30 MOA scope rail might be a much better choice for shooting a .22 rimfire out to 300-400 yd, but there might be a price to pay for having that much cant in the scope rail in terms of zeroing at closer range.
FWIW - the scope turret click value (i.e. 1/8th MOA versus 1/4 MOA) really has little to do with the overall elevation/windage adjustment value, which is
largely dictated by the diameter of the main body tube; 30 mm in the case of BR, NXS, and Competition scopes. My advice for buying any of these scopes used would be that the NXS scopes are probably your safest bet. I personally would avoid the 12-42 BR scope simply for reasons of limited elevation travel and the front parallax adjustment. I would also avoid the Competition scope, because I know the commonly-used reticles in those scopes to be far finer that comparable reticles in the older NXS scopes, and I simply can't see them well enough to use with confidence any longer. However, if you're really interested in a Comp scope, my suggestion would simply be to get a look through one before you buy, just so you know how the reticle appears to your eye. The glass on the Comp scope is clearly the best of the bunch, so no worries there. Another consideration regarding the 8-32 NXS scope is that it is no longer made with 1/8th MOA turrets, only 1/4 MOA. If you buy a used one, be sure that you're getting one with 1/8th MOA turrets, if that's what you want. Finally, the 12-42 NXS would be a good choice, but they have been discontinued for some time and you don't see used 12-42s very often these days. Nonetheless, if you came across one with an NP-R1 or NP-R2 reticle and 1/8th MOA turrets for a reasonable price, I wouldn't hesitate to buy it.
One final suggestion would be that there may also be
new scope options that could work for you. Sightron would be one example of a scope manufacturer that puts out quality products at very reasonable prices for the features they possess. If you have some idea of how much you're willing to spend, it might be worth looking at a vendor such as EuroOptic or Sport Optics to see what they might offer in your price range. Both have features that allow you to input a variety of different specs to narrow down the list of scopes you might want to look at. If you find something that catches your eye, chances are good that someone here can provide a first-hand review for many current offerings.
