JimmyB,
I've seen your posts on the forum, here, asking about couplers there... but have you aired your desires in terms of scale, and type of locomotives, or era?
I see you mentioned a Bachmann steamer.
Where do you want to go in terms of scale, country, era?
This would help answering your questions about curves, grades, couplers, etc.
For example, I am 1:29 scale USA mainline class 1 railroads, mostly Santa Fe. Since I run long trains with multiple locos and want my trains ready to go on a moment's notice I run DCC, and have stainless steel rail, all my desires translated themselves into decisions about power, couplers, grades, rail material, etc.
Greg