If you hipass on the bus you will only flip it once.
In a case of dual tracked guitars panned hard left and right and sent to a stereo bus with EQ on it, won't you flip it once... on each side ?! (left and right).
To me it's totally the same as hi passing on each track, minimal phase EQ or not, that's not the point.
It's all about mono processing 2 hard panned track VS stereo processing them on a bus, and in the case of a standard EQ/filters it doesn't matter.
Do the test, bounce both methods in stereo and flip the polarity on one, you'll hear if there is anything left.
So... you can HP your guitars the way that suits the most your workflow (just don't HiPass twice, on the tracks then on the bus).
Personnaly I prefer doing this on the bus, as to me the HP filter is more of a global thing for guitars and I'll end up setting it exactly the same on each side anyway, so it will be more convenient to adjust it in one move for both guitars and be able to hear the effect on the whole mix.
About compression, it's indeed totally different as a compressor is dynamic dependent and won't react the same (unless your compressor is able to use dual mono processing, and is fed by hard panned tracks).
In the end it depends on the effect you want to achieve, ie pumping the whole bus depending on the whole stereo input (linked stereo compressor on bus, which will narrow a bit the stereo image), or just pump each guitar track independently (unliked stereo compressor on bus, or same compressor on each guitar track).