Sorry , I misspelled molding.
I use shoe mold unless the customer asks that the base be removed.
.
I don't like the "base shoe" look and would rather have base at full height above the floor.
I could see on a remodel where you might want to leave the existing base and then add base shoe.
It's all personal taste, I like the cleaner look of just the base and a cleaner interface with the door casings.
Glad someone mentioned using a Multi-Tool for cutting off the door casings. This tool was a boon to floor guys.
The stair mention was about the added height to your last riser with the new floor covering.
Unavoidable unless the entire stair is re-done....not practical in most cases.
There may be other new floor interfaces to deal with like existing thresholds, door bottoms and lower floor surfaces.
Use the roll underlayment....several brands like Quiet Floor.
"All edges supported" on your plywood subfloor....no plywood butt joints unsupported.
Get your fat guy buddy to walk around and identify any floor squeaks and soft spots that need to be taken care of.
Thoroughly think through which direction to run the new flooring.
Often one way makes the room look bigger and the other makes the room look smaller.
Some rooms like a corridor, look better "long way".
An entry area might look best with the flooring running away from the entry door instead of across it.
If you have to change directions, make the transition at the center of a door bottom or other natural break, if any.
Mark your joist locations.
Use random locations for your flooring butt joints.
A uniform "stair step" pattern does not look good at all.
Use (rent) a bona fide hardwood flooring pneumatic nail gun. This is a mallet-actuated gun.
