I tried making vobs with 2 audio streams (other being dts 5.1 and other being good old pcm stereo) according to this
guide https://www.videohelp.com/forum/userguides/169251.php
which used Ifoedit and Dvdlab, but
the vobs that came out from IfoEdit were totally out of sync
and the audio was full of cuts :S

What software/methods are there for creating
a dvd with 2 different audio tracks (or even three...Wav, DD, DTS?) ?

I've tried Ifoedit +dvdlab and checked a demo of Tmpgenc dvd author
(which I did not notice to have a support for multiple audio streams ??)

The audio + video are in sync on tmpgenc dvd author (so there's nothing wrong with them..Ifoedit just ..jazzez them up for some reason)