.m2ts files?

So i'm starting to make Blu-ray discs using Sony's DVD Architect. I'm trying to find out what file I need to convert my videos into so that they can easily be made into a .iso file to burn onto Blu-rays.

I've been told that AVCHD is the way to go, and not MPEG-2. I know both are good, but that AVCHD gets better compression quality with smaller sizes. Which is good for me because I've got 3 hour long videos.

I notice that the files that go onto the Blu-ray are .m2ts files. Should I be exporting my videos out of FCPX using Compressor to create .m2ts files? If so, how?

If not, what file is recommended to make? I know DVD Architect will convert files to conform to be the right format to make the Blu-ray, but it takes forever when it has to do this, so it's probably better to just give it the right files first. Kind of like how i'd make the files for DVD Studio Pro instead of just giving it a .mov file to convert itself.

Anyway, if anyone can help point me in the right direction that would be great. Thanks!