Pas Vizsla was even voiced by Jon Favreau, who also voiced Pre Vizsla in Clone Wars.
IIRC Death Watch and the name Vizsla was something that already existed before Clone Wars used it.
In canon, they really haven't gotten into that (yet.) In the EU, yeah, Death Watch were part of Jango's backstory and "Vizsla" (later retconned as "Tor Vizsla") was it's leader. Mostly just in a mini-comic that was part of the Dark Horse tie-in push for AotC.
Later, when TCW introduced Mandalorians, Lucas integrated a few details like the Death Watch name and making it's leader "Pre Vizsla" as more of a nod, than anything. The context and execution of either versions bare only a passing resemblance since the former is a faction in the Civil War that took place a generation prior to the Clone Wars, while the latter was a terrorist organization agitating for a more religious fundamentalist direction in opposition to the current pacifist philosophy.
It gets a little muddled of course since the EU was still around for most of TCW's run, and the EU was always retconning itself to align with canon, regardless of a previous story's original intent (and another Vizsla ancestor even shows up in SWTOR as Shae Vizla, AKA 'Mandalore The Avenger') so later stories try and reconcile both versions. Hell, IIRC even those aforementioned tie-in comics for AotC were themselves retconning previous versions of Boba's backstory involving Jaster Mereel, The Protectors and Concord Dawn.
Bottom line though; in canon, while The Death Watch as an organization was a growing problem for Satine's regime, Vizla's involvement with them was only uncovered during the Clone Wars. Given that he was granted governorship of Concordia (conveniently where all the warrior clans that refused to disarm were exiled) it seems unlikely that House Vizla openly opposed House Kryze during that last Civil War. Equally unlikely that Satine knew hose Vizla still possessed the Darksaber; that was probably a closely guarded secret until they were ready to show their true colours and make a claim for the throne.
There's still a lot of unanswered questions of course; who were the opposing faction, how Bo Katan and Satine ended up on opposite sides (not to mention how after a year with Satine on Mandalore in the middle of that very conflict, how Kenobi had never even heard Satine even had a sister), how the war ultimately ended, or why it even started in the first place.
I can put forward a few guesses, but that's all they'd be: -
Specifically that the belligerents in said civil war weren't an opposing House, but a faction of House Kryze itself, that Bo Katan is Satine's
half-sister and that dynastic split is at the heart of the schism. I'd also say Vizla even openly backed Satine's claim, all the while keeping both Bo Katan and the Darksaber as their sylops in the hole, knowing the beaten, bitter and leaderless warrior clans would be easier to control after the Kryze warrior faction was eliminated.
