You sir are a freakin' ROCK STAR!
Hardly - I'm just an old fart that likes to help people out.
Is there a way to make the render in the viewport behave like the "real" render - so I don't have to keep kicking off and killing renders when I see an issue?
Well, sometimes.
The Sub-D levels for the viewport and for rendering are controlled by this set of parameters:
In theory, you can dial up the viewport settings so they match the rendering settings. In practice, I've found that doesn't always work 100%, so I suspect that there may be other differences between viewport rendering and "real" rendering that aren't controllable.
Note that different figures and objects have different defaults for their subdivision settings. It's possible that the clothing you were using wasn't set to subdivide when rendering - it's possible that if you bump up the "rendering" subdivision level for it by one that the problem will be reduced or go away as well.
The core idea here is that all the objects are made up of triangles and rectangles (a.k.a. "quads"). Thus, the "real" figure is "faceted" - there's no such thing as a "true, smooth, curved surface." Run-time subdivision of the mesh helps more properly approximate a curved surface by breaking up each triangle or quad into smaller ones, and then "figuring out" what the local contours look like, and arranging those smaller facets to follow what the program thinks the overall shape is "supposed to be."
The problem of course, is that the facets on the garment don't necessarily line up with the facets on the figure, and so when the two are processed separately, you can get different results on the two sets of contours.
Aside from a "push modifier," the other option that sometimes will address this is a "smoothing modifier." A "push modifier" just displaces the garment outwards, period. The "smoothing modifier" both attempts to smooth out irregularities in the garment as it is currently posed, but also has "collision" settings that will try to detect the case where the garment is intersecting with the underlying figure, and displace just the "colliding parts" outward. So that's another alternative you can consider trying. Frequently, if the smoothing modifier is having trouble handling the collisions, dialing up the number of collision iterations will make Daz Studio work harder at "fixing it."
So, that's kind of the view of the landscape on this particular topic.
