“STEM” is a broad area. Biology is significantly different from computer science, for example.
Calculus BC over AB will likely advance a semester in college math, if needed for your major (of course, it depends on your AP scores).
Another year of high school Spanish will likely advance a semester in college Spanish (colleges commonly have placement testing or procedures even if you do not have an AP score). Will you be aiming for a career where better knowledge of Spanish can help (e.g. health care, civil engineer visiting job sites, etc.)?