Just retested to see if the large PQ issue had been resolved, and spotted something else.
Created a new PQ with 1000 caches. With cache radius selected in settings, app still crashes. That's fine, as I know not to select the cache radius option.
However, with cache radius deselected, I then selected 'save offline list and maps', and then 'maps only'.
My first attempt, with 'only around cache radius' not selected, indicated 120,159 tiles and an estimated size of 1.8 GB. So I decided to select the option, to hopefully reduce the file size. Result was a significant increase (176,000 tiles - 2.64 GB). I cancelled both downloads.
I suspected this was because of the relatively high density of caches, possibly resulting in any map tile being downloaded more than once.
So I zoomed in and looked at a section with 60 caches, but this time saving visible caches only. Similar results (actually worse) :
without around cache radius - 838 tiles, 12.6 MB
with around cache radius - 6720 tiles, 100.8 MB
I did download both, and the second download was much bigger.
It isn't obvious if this is a bug, or a consequence of downloading a dense area. Maybe, a warning in the help section will suffice.