Well, you're starting to get into questions that I'm not all that knowledgable about.
As for manufacturers, I've been getting the impression that they are uncounted and mostly unknown to us. The importers, maybe, just order from whoever can ship right now.
Though maybe that's not true of, say, Grubee. Maybe he sticks with one or two sources.
As for the rubber mounted sprockets, they do have one advantage. If you ruin a wheel, it's easy to switch. 26 in mountain bike wheels are a dime a dozen. I have two MBs and I'm on the second wheel on each of them. If you went to the trouble and expense of a better set-up and then bent the wheel, that might be more heartbreaking.
At 250 lbs you're not exactly huge, but you're a little heavy. I'd say that your choice would be either spend some big money on a bike that's tougher than average or get an average bike and ride it gently. If it were me, I'd go cheap and gentle.