I tried the suggestion in the link to Run as Administrator (selected through the .exe compatibility properties so it stays that way) and it's been running pretty okay. Had a fairly long play session today and got through all of post-choice/Start of Act II Minrathous (no more side quests available, including the Pinnacle of Its Kind), the first revenant, and most of the initial Hossburg area (only the second champion, Pinnacle of Its Kind, and general exploring/area unlocks left) without crashing, or even stuttering.
In shorter sessions I had some stuttering, but when I checked Task Manager to see what was taking resources, "Service Host: SysMain" was taking a lot of them. I get the feeling something was trying to update despite having all settings I can find set to "when system is not in use".