Q 634 & 635 & tank trains; which route?

What numbers? Robert already gave you the answer; any trains bound from PA west are going via Buffalo/Selkirk/Water Level.

These are K trains, not Q trains, they're literally listed in the link you provided.

Sure, but why send the train two states in the wrong direction on a more difficult route?

A derailment is about the only option that makes sense, it would still make more sense to route via the tier/D&H, with what little traffic they have.

"Not wanting to do business in NYS" makes absolutely zero sense, given the three major yards CSX operates upstate, and the fact that they're running close to 40 trains a day between Buffalo and Selkirk.

Outside of combining say, a pair of ethanol/coal/etc. trains, unit trains wouldn't do any switching between terminating points.

Crews can be taxied anywhere, either the train gets delayed or it doesn't run at all as "scheduled" between points that day. That exact situation happened with I007 on Christmas Day, and it didn't run. A crew shortage isn't going to reroute a train on a class I.

Local regulations? Federal regulations governing railroads would supersede anything any town could attempt to put up, other than something like denying construction of a new terminal, which certainly doesn't apply here.

And yet, they're still moving thousands of cars a day on who knows how many trains throughout the whole state, and at a far faster rate than NS, who can't even move a single EB manifest from Bingo to ED in under 3 days with less than a handful of other trains to compete against.

The Q trains only go to Selkirk, which makes even less than zero sense to needlessly route three states in the wrong direction. Both trains cleared Fairport prior to 1230pm today on the Rochester Sub.