I have two of the Black Widow G26s, they’re pretty nice. The real weapon is a decent concealable firearm. “…Best (And Most Deadly)…”? - hyperbole has been part of gun writing, as long as I can recall.
A bit behind the curve, I recently picked up a copy of European Counter-Terrorist Units 1972-2017, by Leigh Neville (Osprey Elite 220).
There’s a mention of the carrying of Glock 17s, matched with Glock 19s or Glock 26s, by members of BRI-BAC and RAID. The second pistol may be carried on the BA, and employed after the 17 is dropped (rather than taking the time to reload).
I recommend the book, it offers information and inspiration, including some “old school” kit ups.