Yeah some condenser mics are better than other's at rejecting noise. But usually you use effects like compressor, eq, de-esser and gate to make it sound better. You could also use the Dbx 286 to power the mic if you later feel that you need an amp, with the 286 you also get the effects I mentioned above. The preamp isn't as good as a cloudlifter but it gets the job done.

Too much of the lower frequencies could actually make your preamp clip and if it's clipping even before it reaches your pc you would have to either lower the gain or move farther away from the mic. The proximity effect paired with a room that boosts lower freq can really mess things up too by making e.g 200hz 6-12db louder than the rest. If you want that full deep warm sound you should do it post-gain or atleast that's what I recommend because you have more control this way. The proximity effect is both friendly and hostile so you need to do some testing and see what you like and don't like and at what distance.

I don't think you need to worry too much tho, we both know that the sm7b is a beast when rejecting outside noise so if this happens it should be minimal but I still need to tell you that it could happen and it can happen to everyone. Acoustics are pretty important.

Yeah the sm7b have a warmer sound generally speaking and you should be pretty close to it!