There's usually separate input and output resolution settings in scanner software. I keep the input resolution set at the highest. In Vuescan (the software I use with both my scanners) the input setting is set to "Archive" which defaults to the scanner's maximum. That way I have maximum detail for possible cropping. I save TIFF files, which because they are uncompressed are rather large, but are lossless and best suited for editing. I don't set the printed size in the scan, that's done in CS2 just before printing. The final saved-for-print file can be smaller than the original scanned file. Still, if I was working with a large volume of files at a time I would need more RAM and storage than I have now.
I'm not sure and have never tried to calculate the maximum actual resolution of the V700, but it's more than adequate for the largest prints my home printer can make from my Rollei negs and the dMax isn't bad. I've made some scans on a friend's Nikon LS9000 and at the print sizes I'm interested in there was very, very little difference. If I ever have the need for a really large print I'll just send it off for a drum scan. My 35mm-only 4000dpi scanner and the V700 together cost me less than half of an LS9000.