I used to work with TPKs a lot but VTPK not as much. But the biggest thing was the levels. Most basemaps its pretty hard to tell the diff at like 17 even. Not much detail is gained on those. Esp on say 3 foot imagery you are past the scale of the imagery anyway. You may have a use case but I would at least try a diff level and see what it looks like. Most of my areas by L 15 the files were just massive. Each level makes a huge diff in file size.
It also almost sounds like you are getting some that are not Vector but regular tiles. Have you tried making the VTPK, then uploading that to AGOL and using it that way?
Hope that helps a bit.