You need to decide what your priorities are. Do you want to get big and muscular? Or lean, small and athletic…stop trying to do both at the same time (you very likely don’t have the genetics for it). Bear in mind that you are posting on a bodybuilding forum where most are not concerned about performance other than getting stronger bigger (and leaner at times).
You are 6’2", weigh 175lbs, lean, and are young = very hard to put on weight.
You need to focus on getting your bodyweight up (eat enough), and do minimal energy work other than weight training.
This is bodybuilding 101 - if you don’t think this is important, you’re in the wrong forum 
By all means try out your HIIT for a while, but keep the sessions short, and if you’re really stuggling to put on weight, drop them.