Are Plugins Pre or Post Fader for Aux Sends?

Hi everyone, so I had always assumed that plugins came after the fader, because it *looks* like they do lol. But I've been reading/watching up on pre/post fader re auxes and buses and what I'm trying to understand is at what point exactly are plugins really introduced into the signal flow? I've read that plugins are pre fader on audio tracks and post fader on the master bus and that you typically can't change that design except for with workarounds like putting a plugin on an aux track and sending an audio track to it rather than placing it on the audio track itself, effectively positioning that plugin as post fader.

But what if I have a guitar track with an amp sim etc on it and say I want to split that same DI guitar signal to a 2nd amp sim by sending it pre fader to an aux track loaded w/ another amp sim... But if plugins are always pre fader then how exactly do I manage to send just the dry DI signal to that aux w/o that dry signal passing through all the plugs incl the first amp sim on the original audio track? I don't want to run one amp sim into another, but rather parallel process them, so I'd send pre fader to that aux track to give each tracks independent faders, but I'm confused somewhere. I mean, when you send audio from a track to an aux via pre fader, is or isn't that signal passing through the audio track's plugins on its way to the aux, since plugins are evidently always pre fader? And incidentally, it *is* true that a post fader send will have definitely passed through that audio track's plugs, correct?
Ok thanks a bunch guys!