As I'm sure you know, DVDs are standard resolution (720x480). So your video will be high quality but it will also only be about 1/5 the resolution. So be aware of that going in.
Also be aware that a DVD only holds about 70-80 minutes of video at full quality. So the program will have to throttle back the quality a bit to squeeze 90 minutes onto a single standard disc.
That said, just use the Publish & Share/Disc/DVD to output your DVD. The program will create it at the highest quality available.
From what I have read of your question, you are not asking about the share choice under Publish+Share for the burn to disc DVD. From what you wrote
what are the best settings to export to later burn onto a DVD
you are asking about suggested intermediate format for later burn to disc which bring in the matter of Publish+Share/Disc/DVD disc with preset NTSC_Widescreen_Dolby DVD.
Since that is the case, I would like to contribute the following to answer your question as asked. To do that
1. From what you wrote you are working with AVCHD.mts source files. But it is not clear what you have.
a. 1920 x 1080p60 which would be 1920 x 1080 @ 60 progressive frames per second
b. 1920 x 1080 60i would be 1920 x 1080@ 29.97/30 interlaced frames per second. This "60i" represents 60 fields per second.
With this information we can suggest that preferred choice for the intermediate format for the Timeline destined for your DVD-VIDEO Widescreen on DVD disc.
Any questions or need clarification, please ask.