> I already have ROIs defined, so I don't supposed I will begin with 1dGC and
> a single seed regions. Is this ok?
That's surely fine because 1dSVAR contains the functionality of 1dGC even if that's what you're looking for.
> I just wanted to confirm that it is possible to perform a second-level group
> analysis (using 3dMEMA, for example), as is alluded to in the paper?
1dSVAR can perform group analysis in the same fashion as 3dMEMA. You will see the options when you have the data and go through the steps.
Gang