Hair transplant to lower hairline after browlift?

Yes, but you need an exam by a doctor to establish a diagnosis (make sure there will be no further hair loss), before considering surgery.  In general, hair transplant surgery works well for what you describe.

Yes, it's possible to get a hair transplant after the browlift.  I have a lot of experience treating and hiding scars in patients who had facial plastic surgery elsewhere and wanted treat their scars.

This is something I have done many times as the forehead gets too wide and the women (usually women) want a lower hair line and the brow lift itself may restrict the hairline lowering surgery. This is a standard procedure that we do almost every day in some form as shown in the photos of 4 women on our website below in the web reference who had it done (none had a brow lift however).