@KittyMcKitty my right knee certainly does not love Bulgarian lunges! I tend to modify quite a bit or do them bodyweight due to this.
I'm in the fb group and many people do repeats of Iron with increased weights. I've moved onto Endgame. I'd say that as well as being longer it's a bit faster-paced and there's more compound movements so I often need to drop my weights compared to what I'd do for Iron. The format for each week is either two upper body, one lower body, a full body and a HIIT or same but one upper body and two lower. I find the lower body and full body pretty cardio intensive as well.
I've not used the app yet as I'm still getting plenty of mileage from youtube but people seem to be loving it, I'll definitely sign up when the promised Iron 2 lands.