Everywhere I read it says that the basic game is done after killing the bad guy; I need to complete all quests, visit everything, etc.  How does one proceed to the WM1 and WM2 expansions?  Should I go there before killing Thaos?  After? Does it matter?  What's the preferred progression path?

 

Thanks!

Go anytime before entering the final pit. It's your choice but WM1 is more or less intended for midgame, WM2 a bit later. 

 

The game automatically creates a save before entering the pit, so unless you delete it deliberately, you can always pick it up there and do the expansions. 

I had fun starting WM1 a little early, to get going with Soulbound weapons, but then it was also fun to begin both expansions after the main game (but before the final battle), because then my priest was super buff and I declined the pop-up to increase the difficulty. 

 

Also, why no more mod power, do you still have a healing factor, or heat vision, or something ...