Yep, you're both right!
Advancing the cam makes the power start sooner in the powerband, putting more torque where you ride more often. The post-1975 cams were retarded in inlet opening timing (and extended out the other side to preserve duration) for 2 reasons: one was to reduce emissions at 2500 RPM, which was the "smog" test in those days, and the other was to increase the peak HP a little bit to make the lower-geared post-1975 engines feel a little more powerful.
With any given cam: you can move the cam forward or back a few degrees and shift the powerband's peak in that direction. If you go "earlier" (lower RPM) then the powerband spreads out over a wider RPM range, and vice-versa. There is a limitation to this, which is based on how soon the exhaust valve opens, vs. the intake closing, beyond which you may have to use a different cam to get the power profile you want: hence the 20 different grinds from makers like Megacycle, Powroll, Action Fours, and the like, all for the same engine.
Using the K0-K5 cam at OEM opening of 3-5 degrees will make power start at 3500-ish RPM and run strongly to 8000 RPM, peaking around 7600. Using the F0-K8 cam (not the F2/3) at the OEM setting of 0 degrees will make the power start at 4400-ish RPM and run to 8500 RPM, but with a higher peak HP (almost 2 HP more) at 8200 RPM. The tradeoff is: below the "powerband start" point, the bike tends to feel sluggish. In normal city riding, "throttle snap" is desirable, so moving the K0-K5 cam forward, say 3 degrees, will make the power increase at 3000 RPM, while the peak also moves forward to around 7000 RPM, but the peak HP is a little lower (torque is stronger through the lower band, though, this is the tradeoff) by a couple. Same can be said for the post-1975 cam.
The F2/3 cam has more lift and duration, riding on the F0 profile, with bigger ports and valves. This makes things very 'peaky', leaving a listless feeling to about 5000 RPM, and a stronger feeling to 9000 RPM. It is hard to ride this kind of RPM in city traffic, and it gets annoying when touring: I remember well those 750 riders who traded in their K2-3-4 for the F2 or F3 bikes and then griped nonstop about this issue...eventually moving to a lower-RPM touring bike of some sort (for the most part).
If the cam profile is altered, the power moves with it, just like the advancing/retarding of the stock cam. If the duration is increased (and the piston crowns and compression increased correspondingly) before-and-after the original "center" timing, then the power peaks stay in nearly the same RPM ranges, but the power increases overall. Where things often "go wrong" here is with the compression: increased cam-open duration lowers the compression if the same pistons are used, so this needs to be considered when plunking in a cam. In the case of the Webcam 41a, for example, if it is installed (and your rockers somehow survive it) over stock pistons, the effective compression ratio drops to about 8.8:1. So, if you install domed pistons to solve THAT problem, you end up with narrow valve-to-piston clearances, which makes cam builders want to sell you heavier springs to ensure the parts don't get too friendly and make other parts...
For all these reasons, it is often simplest (overall street use) to use the nominal Megacycle-like cam in the 125-00 or -04 profile, which is a modern clone of the famous "race kit" engines from Yoshimura, back in the day, if you just want to feed, say, 836cc a little better without boring in new, larger, intake valves to let the new cubes breathe. Their idea was to take the 750 as it was, increase the breathing 10% on both ends of the RPM range, then raise the compression back into the [very] low 9:1 range, all so that the rest of the engine would not be overstressed, thus requiring a bunch of fancy mods. R/C Engineering showed everyone the way to increase the crankcase strength so bigger cams could be effectively used, along with turbos, blowers, etc., and the rest of it is history!
