Could you post the settings you used for AVCHD?
After editing, you choose Share > Create Video File > Custom. In the dialogue box which appears, in the Save As Type window select MPEG Transport Stream (*.m2t).
In the new dialogue box which appears, click on the Compression tab. At the very top, change 'Media Type' to NTSC HDMV. Then below that, change the Video Format to H.264 video and tick the AVCHD box below that. Change the bitrate to, say, 16,000 kbps. Go back to the General tab and make sure that 1920 x 1080 is selected, as well as Frame Based under 'Frame Type'. Then click out. Give the file a name and proceed.
Incidentally, since you mentioned DVD, I have just converted one of the files to an NTSC DVD-compatible mpeg-2, again using Frame Based. (And before you ask, I used the same procedure as above, only selecting 'MPEG' as the format.) And the result was not too bad. Try it for yourself and see if it is OK...