For Transfer Students / STEM majors. How much higher does your GPA have to be than the minimum ?

Again, it depends on the school and specific major.

For example, in state transfer applicants to SJSU in 2018 needed a 2.0 to get into materials engineering, but a 3.6 to get into computer engineering.

http://www.sjsu.edu/admissions/impaction/impactionresultstransfer/index.html