Is it grandpa-tier to tuck your shirt/sweater and have your pants high up?
I think it looks much better than the low pants untucked shirt meme we see today desu
I like having my shirts tucked into my pants, for some reason. Not only is it convenient because you don't have something in the way between your hands and pockets at all time, but I like how it looks too.
I don't think it works all the time, however - as a general rule, I'd say don't do it if you aren't wearing a belt and if the shirt/polo is more complex than a single plain color or eventually horizontal stripes. Anything more than that - a graphic t-shirt, for example - just doesn't work, tucked in.
Also, you probably should have the body for it. It generally works best if you are kinda /fit/ - not even a lot of muscles, just having the general V shape and arms not too skinny. Oh, and you have to be really confident about how your ass looks, because it *really* accentuates that.
As for the pants, I don't really wear them particularly high. Like in OP's pic, I guess.