Does a 4.0 just mean all A’s (low A’s too such as 90’s)? Or is it a cumulative GPA of 93 or higher?
Depends on the school. Some schools consider an A 90+, usually with no plus or minus grades. My high school was like that. Some schools have plus and minus grades, so an A- might be 90-92 and an A 93+. Some schools even have A+ at the upper end of the scale. It’s variable.
In any case, for a 4.0 unweighted GPA you must have all A’s, whatever an A is considered. Directly converting percentage to GPA without averaging each class individually does not work.
It is dependent on your school and you should ask your guidance counselor how your high school calculates GPA. However, for all intents and purposes a 4.0 is generally an A grade and above (93+).