Welcome to Grim Dawn.
As a fellow HC-exclusive player with a similar background (D2 and D3), the biggest tip I can give a new Grim Dawn player is to read up on armor absorption as it is an easily missed stat.
Beginning with a pet summoner build is pretty forgiving and the “Fluffy” conjurer build that you referenced is actually the easiest build that I have personally levelled to 100 (and is still alive). Note that true pets do generally draw aggro away from you whereas “player-scaled pets” do not.
Further down the track you might want to look at other builds such as those by RektbyProtoss here [HC] Build Collection by RektbyProtoss
Good luck with your HC journey.