Protein that contains just protein (I.e. no carbs) is fine whenever your diet phase. I think the issue becomes what and when you consume and with what. You don't really want to be taking EAA other than preWO, but whey or
casein is fine anytime other than this.
Mass gainers IMO are expensive junk, as you would be better off eating real food.
Leaning down is more about regulating your caloric intake and getting a good balance of nutrients. Look into keeping a food diary and work out what your daily needs are. Then start eating sub-maintenance. I'm in Aust too and am signed up for a fitness/weight loss challenge. I plan on losing a bit of flab by limiting my junk calories (non-food calories like lollies and soda) and actually doing some cardio