Suiting Essentials pieces are sold as separates, so you can get pretty much any chest-to-waist drop you want.
It's basically the BrooksEase concept in the BB "in-between" (Regent) cut [Fitzgerald being their skinniest cut and Madison the biggest] with a woolen fabric that has a dash of synthetic in it for "stretch."
The 1818s are made of more expensive fabrics, usually Super 110s in very fine twills, whereas the BrooksEase/Essentials lines are plain-weave.
Some 1818 fancies are made in Italy; the standard 1818s they always carry (solid dark gray, solid navy, etc.) are US-made.
TTBOMK, all the US-made BB suits below the Golden Fleece line are made by Southwick (Grieco Brothers), an old-line and well-reputed Massachusetts company which BB's parent (Claudio del Vecchio's Retail Brand Alliance) bought recently and is now reportedly in the process of moving into new facilities with state-of-the-art technology, etc.
BB has long had its own shirt and furnishings plant in Garland, NC, and its own tie plant on Long Island, and has had success with both. I suspect the Southwick buyup and move is part of an effort to build on that model, and also to secure the future of one of BB's key US suppliers (the pool of these has been drying up in recent years, such as when Hartz-Oakloom, long a maker of suits for BB, had to close up its two plants and go out of business a few years ago. I still miss going to their Frederick, Md., factory store).
As far as the Essentials line goes, I don't wear them. I like the single-pleat trousers, but in order to have the coat fit me in the shoulders and upper arms, I have to size up to a 50, and then it's very baggy around the waist. With some tailoring, I get a much better fit by buying the BrooksEase in a 48 coat. But YMMV.
My last BrooksEase I got the day after Christmas for about $350, which I think is a snip.