Yes, lower than factory.
Here's the thing. Larger bars have much higher spring rates. Higher spring rates mean less suspension travel, regardless of how much is available (distance to the bumpstop). So, if you double your spring rate (like most 1" bars do vs stock) then you can pretty much figure on using half as much travel in most situations. So, even if you lower the car and "use up" some of that available travel, it's not a problem because you still won't bottom the suspension out.
I'd be surprised if my duster has 2" from the shorty poly bumpstop I put in there to the frame. But with the 1" torsion bars, I've never even been close to bottoming the suspension. Tops of the tires are just covered, and they're fairly short 225/60/15's.
As far as needing drop spindles to get low enough, it will depend on how the torsion bars are offset. Some are offset more than others, the 1" JS bars are 0 offset, and my adjusters are pretty close to the bottom of their adjustment on my Duster, so I can't go much lower than I am now. Hotchkis bars are offset to the point that some guys can't even get to stock ride height with the adjusters all the way in. just depends on the bar.