well, first of all, thank you :D
Secondly, some of it is fat and water, without a doubt, I think if I've decided to cut to like 69 or 70 kilos I would be able to see my abs BUT I don't want to cut because I dislike how I lose strength during it and I'm pretty okay with ~20% bf
if you want to gain weight and you don't do leg days you should really rethink your approach to training. When I didn't do legs for like first 6 months of my training I barely gained 4 kilos. All that weight and power come from your legs.
Also the reason I gained so much is probably due to the total absense of muscle. I mean, my height is 178 stable for two years now, and when I was about to start, my arms were like 11 inches, now they're 15 inches :B