The above image of bk-2C-B-NBOMe is missing the letter "r" next to the "B". Br stands for bromine / colliquially bromo (which is the prefix name for the element bromine), B stands for boron which is another element.
bk-MDA, if at all active, would probably need a ridiculous dose like something along the lines of 400 mg if there is ~4x potency loss when beta-ketonating 2C-B. I really don't think it is a smart idea to put that kind of strain on your vitals.
bk-Mescaline even worse, a dose may be over a gram, though it wouldn't be a subbed cathinone like bk-MDA.
The term beta ketone refers to putting that carbonyl oxygen on the beta position. The term beta position (wiki search substituted phenethylamine to find out what it is) is only meaningful in a limited context*. So on terpenes you can certainly 'design' an additional =O carbonyl oxygen, but that doesn't magically create an interesting structure. It only makes sense if you depart from a certain drug that would benefit from the modification.
bk-2C-B may have its fans and the prospect of other bk-2C-X compounds can be fascinating as long as the starting material is not too weak to begin with (which would yield the problems I listed at the start of this post), but that may mostly be by the virtue of cathinone (again look up the structure) being an active compound itself. So there may be some crossover pharmacodynamics - which often don't work well by the way - and quite frankly the dimerisation problem giving inconsistent responses to dosage and the general impotency are a pain in the ass. These problems (not sure which exactly) seem to be causing the drop in potency.
Also prepare to be told by people that cathinones are categorically shitty.
If you like methylone then obviously beta-ketone versions of the MAPBs / MAPDB should be fun, yes I would expect those surfacing first and foremost. Those actually make sense and don't go so far out on a limb.
No offense, I applaud the enthousiasm, but you need to either learn some more chemistry and/or stay more close to home regarding drug design. Ketonating the shit out of random chemicals does not mean anything per se, it is a trivial thing in organic chem and there are other considerations if it's going to be worth investigating any bit.*
(What Sekio said plus where I marked * are reasons why bk-etizolam, bk-kavalactones, etc don't make sense. With some exceptions perhaps, for example 'beta-keto tryptamines' apparently have been discussed, just BL-google that)