There are some pretty big misconceptions about what these stats actually refer to. They are so overused and people think they know what they mean, but most times they don't.
This is pretty straight forward. The large muscle groups are larger.
Although, one thing to note, a high strength person will only look like Arnold Swartznegger if they are also low in dex and con. That's basically the look of someone who is min-maxing strength.
A healthy person with a lot of muscle will actually almost look like they are fat, except not. Bottom line, their muscles won't have much definition.
This is quite likely the single most miss-understood stat people talk about.
For one thing, dexterity and agility happen to refer to 2 different things. Dexterity refers to how competent and precise you are in your physical movements, and how much conscious control you have over your own body. Agility refers to your ability to quickly shift from one physical motion to an entirely different one.
(Think of it as agility is how many times you can stab something with a sword in five seconds, and dexterity is how accurately you can hit one specific spot with each stab.)
In my own stories, I like to use the term "deftness" in order to act as a catch-all that would encompass both of those things.
Neither one of these things would actually affect your physical appearance. You can be fat, you can even be muscle-bound (limited range of motion due to excessive muscle mass.) Those two stats would not be influenced at all.
Flexibility would affect the way you look, but there is usually not a stat that describes flexibility and range of motion.
Constitution refers to the way your body behaves in terms of how well it maintains a healthy state of equilibrium, while stamina is an entirely different thing and refers to how long you can continuously make physical demands on your body.
Constitution, as it is higher, would actually make you look more physically attractive. There is actually a very strong correlation between health and physical beauty. It's almost one to one. A female body would move closer to an hour-glass shape, while a male body would move closer to an apple-chested shape. A 10-7 hip to waist ratio is actually an important aspect to a healthy body, anything different would be indicative of visceral fat which is very bad for you.
Stamina is another matter entirely. It would not affect physical appearance.
This would not affect physical appearance at all. However, higher levels of intelligence and wisdom might lead to having better self-care skills, which would mean you would keep yourself cleaner and better groomed. That is assuming you don't have a logical reason to allow yourself to look like a slob.
So, higher intelligence and wisdom would not have a direct effect on your appearance, but there is an indirect effect in that it will allow a person to have some degree of choice about how they look.
Lower intelligence and wisdom would lead to the opposite. Poor self-care skills, which will cause a person to look rather un-kempt. Would likely put on some weight, look less healthy, and if they are male then they might have some pretty ugly-looking facial hair.
All those things are also possible with higher intelligence and wisdom, but if intelligence and wisdom are high then they chose to look that way. If it's low then they look that way because they didn't know better and just let themselves fall apart.
