There is no guarantee that any one particular disc will play in a given player.
The only time I would use "Fit contents to available space" is I were getting a Data Rate error message from the project in the burn to phase and had to
lower the bitrate manually in order to reduce the file size and get the burn to progress. I would work routinely with a check mark next
to "Fit Content to Available Space".
I see no advantage to what you are doing, and you open the possibility of the data rate error which will force you to lower the bitrate anyway.
As to player compatibility...in some infrequent instances, a player might require an Audio_TS Folder in with the VIDEO_TS Folder of the
DVD-VIDEO of the DVD disc. Audio_TS is not included in the Premiere Elements burn to disc. But, it can be achieved with a Premiere Elements burn to folder
and then using the VIDEO_TS Folder and a home made Audio_TS Folder and ImgBurn to create the DVD-VIDEO on DVD disc.
As for AVCHD DVD or Blu-ray disc format on Blu-ray disc, I am not sure that adding a AACC Folder or the like would make any difference on the playability
of AVCHD DVD or Blu-ray disc format on Blu-ray disc. However, Blu-ray adds another consideration to "Fit Content to Available Space"