No worries, I understand what you’re asking ❤ I could write SO MUCH on this, so I’ll try to keep it short and basic.
We all picture him differently, I think that’s what will make it so hard to cast an actor. I still debate with ppl about his hair: whether it’s chestnut-color (like in movie!IWTV), shorter and curlier (like in Lestat the Musical), or dark, longish and silky as in a lot of the fanart. We all apply our own ideals of beauty (which are influenced by our own cultures, art, families, romantic partners, and/or friends, etc.) onto him. Plus, the other VC characters are generally more poetic when they describe him; they detail his inner qualities more than his physical ones.
That said, I agree that he would appear at first to have an overall delicate and almost androgynous figure, and he moves with a lot of grace and dignity, but he can definitely kick ass when necessary; there’s muscle and skill packed into that slender build >;}
I imagine his eyes as being more of a sea-green, maybe not like lasers ALL the time, but with a sparkle to them,

…with a good fringe of inky eyelashes when his eyes close,

^and that feathery but still masculine eyebrow.

^X these eyes belong to Steven Kelly. His lips are a lot bigger then I picture Louis’s lips, but his jawline is right (it’s a flattering angle tho tbh), and Louis is described as having a narrow head.
As for the body, I picture him as a little underweight due to the state of physical unfitness he was in in the month(s) leading up to his turning, but still muscular:

^X Simon Nessman would probably not like to hear himself called physically unfit, what I mean is, he’s got the basic setup, is a little underweight, not all !bursting! with muscle. (yes I imagine Louis has dark nips like this but a more pronounced happy trial *blushes*)
@eibhlis97 and I agree that he has great thighs due to riding horses all his life ;}
And a view from the back, bc yes, he requires, as you put it: “long legs ( and of course nice butt ).”

^X Louis will wear heels for Lestat on occasion. Very special occasions. Right, @vampchronfic?