Can I assume that i can send the 'sid' stream ID, and if bassenc is trying to connect to a 1.0 shoutcast it will still work?
No, that won't work (BASS_Encode_CastInit will fail), as the old server won't know how to handle the 2.0 protocol.
Regarding other requirements of Shoutcast 2.0, besides what you quoted above (eg. UTF-8 titles), you don't really need to do anything else differently compared to connecting to an old Shoutcast server.