recommended apps for Boox (Max)?

having successfully avoided android so far, I might have to deal with it to my big annoyance as I consider buying a Boox Max. therefore some questions in this respect.

which apps would you recommend or even regard indispensable for the Boox readers? for reading (mainly pdfs, many scanned). for data exchange I think about using owncloud.
or would the preinstalled apps be sufficient?

to what extent can I suppress connections to google? what other app depositories are useful instead? (no, not amazon)