Interesting. I've not used the support brackets in the manner you are employing them. Those that I use are sufficient to support the weight of the sink, on their own, and are installed front to back, thereby eliminating any risk of interfering with the sink fixtures. (There is a large nut on the basket strainer, which needs to be tightened, and that for a disposal, is even larger in diameter). If your hope is to eliminate the need for caulking at the intersection granite slab and the sink rail. You'll be hard pressed to find and installer who will warranty the installation, without a waiver. So, hold the sink as even or below the level of the plywood.

I had a Kohler self-rimming double bowl in my old kitchen. Couldn't wait to get rid of the self-rimming and the double bowl. I did have problems with scratching and staining (after 25 years!). I now have undermount fireclay single bowl, I just thought it was too beautiful. I love, love, love the single bowl! Which ever you choose, get the sink grids to protect your beautiful sink (and dishes)!

The weight of a sink is irrelevant when you install it with a Hercules Universal Sink Harness because the weight of the sink if borne by the cabinets, not the countertop, as it should be. Get the sink you want and insist your installer use the HUSH.

I replace sinks for a living and have yet to pull a countertop to replace a sink except in solid surface. You tap the cabinet front off, change the sink, and put it back on. I've done it twenty times. Did it the day before yesterday. For easiest sink changes, insist that your fabricator strap, not insert fasten, your sink in place with a Hercules Universal Sink Harness (Braxton Bragg) or a Sink Strap (Regent Stone Products) or two. Two easily accessible bolts instead of 12 inaccessible ones. I'd change a strapped apron undermount in a hour at most. Make sure he puts a nice radius at your sink cut-out too, 3/8" minimum. No pencil edge, please.