I'm a big proponent of rolling instead of carrying whenever possible. There are situations, though, like boarding transit or surmounting apartment stairs, that will necessitate lifting and carrying the bike.
Yes, but I am not sure yet if this is the case for the OP. Boarding transit (at least around here) is done by just lifting it. We can roll the bike (on its wheels) all the way up to the bus or train but I know this is not possible other places but rolling a folded B innside the cower should be possible most places.
Apartment stairs- yes of course but a lot of peopel can hang the bike with the seat on the sholder and just walk up or use an elevator.
The Op said "..and I do plan on hauling the bike folded on my back so weight is also important to some extent".
That is not enough info really. Guess he`ll be back with more info.