Is there a buffering difference between increasing and decreasing stream quality?
1) It depends mainly on the streaming protocol. For HLS and HDS for example, yes because the player will usually download a number of segments before starting playback, and the download time is proportional to the size of each segment of course. For RTMP for example, the buffer is custom-set by the server which means it will theoretically depend on what the server has chosen for every bandwidth. E.g., it may chose a 0KB buffer for all streams, in which case there will be no difference in buffering time. In more realistic cases, however, I expect the server would set buffers to each stream according to its bitrate, which brings us back to what happens with HLS or HDS.

Note that the difference in buffering time really depends on your own bandwidth. If you have 50Mbps internet speed, you won't feel any difference whatsoever since it would be the difference between downloading ~3MB of data vs ~2MB/~1MB of data. Of course if the server is setup improperly and has high latency, then your speed means very little and you will feel a difference.

2) No because as far as the client is concerned, a livestream is basically the same as a prerecorded stream (apart from the fact the server may let you download the stream faster than you can see what you download, aka faster than real-time).