Window Frames Pulling Away from Wall

I am wondering what to use to seal air leaks around window frames. Most of the articles I've found addressed sealing them from the outside of the home. But I need to do it from the inside because the actual wooden frames have pulled away from the wall (sheetrock) over the years. Gaps are only 1/8" - 1/4" wide. I assume I should use caulk, but which type? I don't know how to "finish" the project so ugly white caulk isn't visible each place I've done. Do I simply paint it afterwards? If so, what type of caulk is best? Thanks