It’s possible, but it’s not documented as it’s not ready for production. (Mainly because the reasons what you mentioned: QUIC is not supported everywhere and you may get too many nodes without QUIC support → increased latency or even failure).
You can try to set environment variable STORJ_QUIC_ROLLOUT_PERCENT=100, and test it. (but use it your own risk ;-), worst case it will be slower or failed download)
This is strange. We don’t have 60k nodes, so it means that you have more than one connection to each storagenodes.
One single download requires a connection to the satellite + connection to 39 storagenodes (after downloading data from the fastest 29, the remaining will be closed).
So 60k connection means at least 1538 segment (= files for small files) download.
I guess this tool tries to download data massively parallel.
One option is increasing the connection pool with this function: uplink/private/transport/transport.go at 72bcffbeac33146027b0f70fc6fcd703fdf8bfb0 · storj/uplink · GitHub
The default size is 100, which is very low. you can even use 5000-10000, which will increase the performance but also increase the memory usage…