Confusing access of Dropbox files when compared to different cloud providers

I often get very confused accessing my Dropbox files via various Apple, Google and Microsoft apps on my Mac and iPad. This is particularly problematic for me when trying to locate and open files on Mac and/or iPad for Microsoft apps (such as Excel & Word), for Google apps (such as Numbers & Sheets), and for comparable Apple apps. For example, some .xlsx and .docx files in my Dropbox will open from my Mac, but I'm not allowed to open them from my iPad. And sometimes vice versa. Some Dropbox  files don't even appear on both my Mac and iPad, for reasons I don't understand. I wonder if this may be the result of confusion around rules to ensure proper software account integration. Or perhaps that syncing in the integration world get too complex to for casual users like me to understand or manage. Is there a single document available that explains all the steps necessary to make sure Dropbox will present a standard, consistent list of the entire file content of my Dropbox to the same apps on my Mac and iPad.