Yeah... low G just means the top string, your G string, will be tuned down an octave. So no more re-entrant tuning, and that open G string still plays a "G." The G string will be the lowest string on your uke, rather than the C string. This tuning is, in fact, the bottom four strings of a guitar, only shifted up a perfect fourth (five frets). Chords are played exactly the same, except all notes on the G string will be an octave lower than they were on standard high G re-entrant tuning.
The voicing of the chords will change slightly, but as Boozelele put it, a C will be still be a C, and an Ebm7 will still be an Ebm7. You play them exactly the same, nothing changes. Same chords, performed identically. But whatever's being played on the G string will be an octave lower than it normally is.
Also, in response to the OP's concerns regarding intonation, I put a low G on my tenor just to try it out, didn't much fancy it after the strings had settled (not the best brand of strings for this uke, I suspect), and swapped it out for a high G at once, and have no intonation problems to date. As far as I know, while a tenor uke might come strung with low G, I think they're all made for high G re-entrant tuning. I could be dead wrong, though... point is, if you buy a uke in low G and re-string for high G, you should be fine.
-Tom