For the most part music label contracts with a streaming services do not allow them to sub-license offline mode to partners.
I’m not sure how to answer this question. Both services are distributing audio in essentially the same way from a technical perspective, so I can’t explain your subjective differences. Roon handles both the same in terms of buffering. Our buffering scheme is more aggressive than I would expect to find in either of their clients (on the flip side, it is also more demanding on weak internet connections, because we do more read-ahead…always a tradeoff).