the thing about beards can be genetic, if you take a look at the etnies you'll see that not all in of them the male full beards are the rule
I don't have a full beard also and Im 22, I think I never will
Im skinny too and don't gain weight and Im perfectly confortable with it, its just genetics dude
I know you may have perception that those ones with more mass and beard may feel kinda of more masculine for something, truth is, most of them will get fat and bald... and will be hating their beards for having to shave it everyday
my legs are fine, but I think it has more to do with how you grew up, I played soccer and basketball when younger and I always accepted this as the reason because some friends who are just as skinny as I am, or in some cases, fatter/fat and have legs that are skinnier/proportional skinnier
but I think you're worrying too much and this can even be some kind of paranoia or something about your perception of yourself and can affect your self-steem BADLY, in that case what I'd recommend you is a psychologue!
do this, go check your T level, then get your shit straight, try to work around what you feel that could be better but don't go thinking that you needed to change your constitution/body type
rockstars don't care about this things and still nail all the chicks!
ps.: its a picture of me as a rockstar, but I was not nailing this guy!