Hi there,
Frankly speaking, combined with my own experience converting bunches of MTS files, I would like to introduce u a powerful program called Aunsoft MTS Converter for Mac recommended by one of my best friends. It works very well in directly converting MTS/M2T/M2TS/AVCHD to MOV for FCP. Moreover, this software enables users to remove the interlace issues of camcorder videos in an easier way. Also hope it will really help you out.
https://www.aunsoft.com/mts-converter-mac/
Cordially urs,
Jessica Gates