Extent of accuracy
Question: Is it better to tell the EXACT height and weight or should I just state roughly?Answer:
I think it depends on your narrator.
If you are writing in first person or third person limited, you have to consider what details your character is likely to notice or have in mind.
Everyone has a different set of knowledge and interests.
For instance, a character who is an engineer or architect or surveyor will likely include more precise technical details about buildings.
A psychologist, on the other hand, might notice the personality quirks of the people he encounters. A doctor might be more alert to someone's medical condition. The vocabulary a character uses shows what subjects he knows more about.
One narrator might habitually look at strangers and estimate their height and weight (perhaps a police officer trained in observation). A child narrator, on the other hand, might just describe people as tall, short, fat, or thin. A main character who is obsessed body image might pay closer attention to other people's physical deficiencies than someone else.
The other thing to consider is your genre. In historical fiction, details of the time and place matter because your reader wants to learn about that period (for instance, were people in a certain era short because their diets were poor?). Fantasy readers like details about fantasy characters. Science fiction readers are interested in the possibilities science offers (e.g. biotechnology). Thriller readers enjoy learning the technical aspects of the main character's profession, whether law, medicine, espionage, etc.
You have to ask yourself what details feel right for the story you are telling and convey a sense of the characters.