Why would you ever want only treble or bass?
From what these instructions say, its not about doing that at all, just about increasing the sound quality... They're connected as normal for now, if I cbf I'll do the bi connection using the single front speaker terminal pairs, but I doubt I'll be able to hear any difference anyway.
As for the sub, the speaker wire option with my amp only having the 1 set of front speaker terminals, I'll go with the AV cable connection instead.