I've been reading about "nandub" and "smart bitrate control". I downloaded nandub and opened it and noticed there is no "compression" under "video" on the toolbar. I also noticed that in the nandub sbc howto guides they talk about divx 3.11 but nothing above that. Does DivX 5 already implement features similar to "smart bitrate control" and is that why I only hear about divx 3.11 in reference to nandub and sbc?
Yep, 4.x and 5.x have the similiar feature (VBR) and therefor it is not needed. Only thing that NanDub is needed at the moment, is to mux AC3 audio into DivX clips. This of course unless you insist encoding with DivX 3.11alpha.