... I think even when talking about someone sending them they still refer to 'summoner' vs beacon?
Yes, I think a "beacon" (as Harry used it) just meant the biggest, brightest, tastiest bit of fear the fetches can detect; but they're already in the mortal realm, or they cannot go after such a "beacon." I don't know that it was even a formal bit of wizard-jargon (like "veil" for invisibility-magic)... Harry's very-fond of just calling stuff by whatever term comes to mind, and "beacon" struck me as an instance of that..
The "summoner" is someone who actually brings them across from the Nevernever.
... Am still thinking the mirrors were the link, as in actual mechanism used to cross like an item in a ritual almost, they focused the energy into one point better.(in the presumed order of operations for summoning, the mirrors just take the place of the circle anyway actually)Though, they're just part of fetch attributes too ...
Harry knows fetches come into the mortal world via mirrors; as you say, "just part of fetches attributes."
In some cases, the mirrors were the link; the bathroom in
Splattercon!!! where Pell got assaulted, for one example: There was Pell, and there was Nelson, and there was
not a summoner (or Pell/Nelson would have noticed). So the fetch got itself into the bathroom through the mirror (and, likely, back out again).
Later, at the screening of the movie where Rosie got injured, Harry's own magical senses could feel someone else's magical working as it went off(*). We don't know for sure, but there's a good chance that was the summoner.
So I think we have a strong case for "both" rather than an either/or situation.
... neither do we know they did 🤷♂️ so that's kinda a balanced point there ...
Not a "balanced" point: I am alleging that there is
no point at all to be made from our info on Fetch-summoning. None of the summons' happened "onscreen," nor did Harry find any summoning-circles. We have precisely
zero info about who summoned any of the fetches, or how. All theories on Fetch-summoning are based upon implied data only, and multiple theories about it are more-or-less equally-strongly (or equally-weakly) supported.
I will advocate for my own WAG, here: that Molly was being nudged towards black magic by Lea, on Mab's orders: to leverage Harry's severe case of
[White Knight Syndrome]
X
[My Best Friend's Daughter]
X
[Everything-Is-All-My-fault Guilt]
to create a Harry/Molly relationship where
Winter already has its claws in. Likely, I think, Nemfected-Maeve got involved (trying to Screw Up Mommy's Plans); I think some of the Fetch action was Maeve's, but mostly it was Mab's (the Madrigal(Darby) Whampire involvement was -- I
think -- Cowl's).
(*) -- In the incident where Rosie got hurt, there were actually
three magical workings:
#1 The power went out. Maybe that was mortal wizard, either intentionally hexing the power, or just mortal-wizarding the way mortal wizards do (i.e. plays-badly-with-tech); given how widespread the outage, my bet would be that it was intentional. But it could have been a non-mortal, too.
#2 The myrk. My bet is that it was a working of Winter (likely Maeve, maybe Mab), because (a) it came alongside a
huge temperature-drop; & (b) a Maeve-likely myrk (& Hobs) was also a Winter Summoning in
Small Favor.
#3 The summoning itself, calling "The Reaper" into the movie-screening. If this was Mab or Maeve, they could summon fetches without any "magical working" per se (when one of the Winter Queens wants a winterfae... they just arrive, no circle, no fuss, no muss).
Maybe that was 3 different workings, as many as 3 magic-workers? Maybe it was one magical heavyweight doing three workings simultaneously (or in quick succession)? I don't think we know...
... So the fetches go fetch Nfectees and then eat the portion actually Nfected, which is why the 'final fetch' seemed so different ...
I don't think the Fetches have enough magical mojo to handle that. Gatekeeper is among the best in all creation at spotting Outsiders: if Mab could station Fetches at the Gates, and get a better hit-rate than she gets from the Gatekeeper (or even just give him occasional time to pursue other Outsider incursions, in other places) she'd be doing that; but we haven't a hint of it.