I've never heard of a lubrication/harmonics issue, but, lots of stuff Ive never heard of. I have heard of running at any given RPM on an engine not yet "Run in"or Broken In & setting up vibrations in the rings & creating problems in the bore. Vary the engine speed. Watch your mirrors & when no one is running up on you, slow it down, a lot, & cruise at a low speed for a bit, a few minutes when possible. There is a place where the bike "Feels" better. A spot that's got less vibration & if you goose it, it still has some accleration left, with torque, not just" I twisted the throttle & i THINK I can feel it accelerating". When I am breaking an engine in, I don't go past that spot for long & I don't do it often. Also, I have been told by a guy who is a pretty sharp mechanic, tho he may be full of it here, I dunno, But,, he says, Get an engine running up in the RPM range, then just slap the throttle shut & let the engine vacuum suck the rings out against the bore & seat them.
Every time I run past the recommended speed during break in, I only go there for a few seconds, then slow down & allow any hot spots to cool. Ride calm for a while, at least 15 minutes, before I would dream of doing it again. I have a Suzuki 650 that runs very nicely & a Moto Guzzi with 4,500 miles on it that seems to be still breaking in. The folks who sold it to me said wait till it has 6,000 miles on it to se what the MPG will be. I hope its like a pocketnife that is hard to sharpen. Once ya get it sharp, it stays sharp.
Good luck on your trips. Yes, the larger sprocket will slow the engine down, which allows you to cruise at a higher speed or cruise at the same speed as before the sprocket change & save fuel & lengthen engine life by decreasing the revolutions per mile.Still, if it's not broken in, vary engine speeds. I dont know how many RPM is needed, so I would vary a lot, unless someone I trusted chimes in.