Sub documents other than ODT

I just started a couple master documents which include the same subdocuments. I currently have then in ODT format but was hoping to have the ability to edit them on an Android device offline. The master documents override the subdocuments header and text body formats for their specific purposes.

Since there is no ODT editor for Android I would have to use either RTF or DOC format. I’m wondering if there are any suggestions about which format to use for this? Is one of these more reliable when included in master documents?

The general answer in this forum seems to be that doc is the format most compatible with odt. I have used .doc documents in master documents without problems. (The problem is when I want to make the end result available to MS Office users again as the odm of course is foreign to MS Office. Save as odt, open and save as doc seems to be the best way.)