Personally I find the health risks of soft drinks unacceptable especially if you want to live healthy. Diabetes anyone? Can't you find a diet soft drink you like? Artificial sweeteners have some bad press but IMHO the benefits clearly outweigh the risks of too much sugar. It's pretty amazing to drink as much as you like without it throwing off your calories of the day.
Yes, a high protein intake is beneficial. First I would suggest that you use a calculator to estimate your lean mass and your basal metabolic rate (BMR).
This one is very accurate as opposed to others which often overestimate the BMR. Its for keto but ketarians are basically eating like bodybuilders. Just ignore the net carbs it shows. Stick to the protein. When you're finished you know how much grams of protein per day would be appropriate for optimal weight gain. The amount of meat necessary can be intimidating but you can use protein powder for shakes as well to hit your macros.
Also relevant is your caloric intake. You want to have a slight surplus of your BMR in order to efficiently gain mass, maybe a 10% surplus. Or you want to be 15-20% below your BMR during a cut. The testosterone will surely help not losing much muscle during a cut btw. For this to work properly it is strongly advised that you track your intake using a calorie tracker app, like myfitnesspal for example.
Now this might seem a bit much, especially the calorie tracking but you can simply scan the bar code with your phone, weight the amount and insert it into your food plan. If you stick to that it becomes second nature after a while and if you wanna get really fancy you can get a fitness tracker and link it to myfitnesspal for even more accurate information.
