Right so first thing to establish is that with Echo, no route is more canon than the others. There isn't a "true ending". In fact, that's actually a big part needed to understand certain aspects of Echo and Arches: There isn't one single timeline, but many branching timelines covering many different possibilities.

The most apparent example of this are the various routes: Carl's Route; Leo's Route; Jenna's Route; TJ's Route; and Flynn's Route. But the Good and Bad endings that some routes have are also examples of this.

Each route in Echo corresponds to a route in Route 65 as well. Jenna in her Echo route mentions that Chase first came out to her before anyone else, but Flynn says the same in his route. Other little details—such as who Chase considers his best friend—also vary between routes but do line up with what happens between Chase and that specific character in Route 65. Specifically, whoever Chase first confides in about his sexuality and the situation he finds himself in at the beginning of Route 65 will be the same character he goes after during the prologue of Echo after the big fight that kicks off the story.

So what we have with the Echo Universe is something akin to a tree: Several "branches" splitting off from each other linking back to the "trunk". This applies to Arches as well.

We of course have the Arches VN, but Cameron and Devon both appear in the epilogue of several routes in Echo: Flynn's and TJ's where they take center stage, and Leo where they're mentioned (as a "bear and coyote") when Chase visits Leo two years after the Hysteria, but not named.

It can be assumed that Cameron and Devon make their way to Echo in the other timelines as well, but what must be noted is that Arches VN and the routes we play through in Echo are in different timelines. Details in every route contradict what happens in and before Arches VN. Things like: Cameron and Devon meeting up with Chase to give a tour of Echo; Duke being killed during the Hysteria; Brian being killed during the Hysteria, the Hysteria in TJ's route happening in 2017; Cameron and Devon visiting Echo in 2017 in Leo's Route all contradict the events of Arches VN, but a version of Arches VN still takes place in each of those timelines.

Going further, as you know there isn't any choices that the player makes during Arches that changes what happens. That's because the timeline split in Arches is written into the story. At the end of Arches when Cameron, Devon, and Brian are in the mines together, Brian has a shotgun pointed at Cameron's head. Two timelines branch off from this point: One where Brain shoots and kills Cameron, who then possesses Devon and leads to the events of the short story Vessels four years later; and the timeline we play the rest of Arches through, where Cameron (who just saw a vision of the other timeline) pushes the shotgun away mere moments before Brian can pull the trigger and narrowly misses being killed.

So all in all, the timeline looks like this:

(I apologize for how this looks. I had to do it on my phone rather than my laptop so it isn't as good looking as my Zelda timelines, which you can check out here if you're curious)

The Echo short stories that take place from January 2010 through October 2014 happen the same in each one of these timelines from what we can tell. There's no evidence to suggest that the short story Runaway in the Flynn Route Timeline is any different from the Runaway in the Leo Route Timeline for example. Same goes for Benefits.

To end things off, these timelines aren't completely separate. As briefly mentioned earlier, it is possible to peer into one timeline from another if someone has any psychic or supernatural abilities. Cameron Wilson is one such person. During the epilogue of Arches, he peers into the timeline in which he died several times, even briefly communicating with that version of Devon and Cameron (who, again, is possessing Devon). In Vessels we get the other side of this: Devon and Cameron—who are reliving their college memories in a psychic/dream plane within Devon's psyche—are confronted by Cameron from the timeline in which Cameron survives. Though this seems to only be a mental thing, as Cameron isn't physically there but his mind and consciousness is.

The Socket Man is another example of someone not bound to one specific timeline. Despite only being created in the Flynn Route Timeline, The Socket Man appears throughout the VN: He kills Duke in Leo's Route; he appears several times in Jenna's Route; he appears in Arches just to stare at Arturo; and even appears before the route split and in timelines that we never play through otherwise.