Hi Alan,
I've written a fair bit about such workflows in articles on this website - if you do a search within the site you will find them, largely dealing with scanning negatives, but the principles are the same. One can approach these tasks in many different ways, but in a nutshell, I would recommend as follows:
(1) For scanning, if you intend to keep using SilverFast, you may wish to consider up-grading to Version 8, because the interface is much, much better, hence a lot easier to work with. The basic functions haven't changed but the functionality has really improved a lot. As well,with version 8, you are OK on any Mac or Windows platform.
(2) I do not do any sharpening or grain mitigation in any scan software. I have two reasons for that: (i) there are better specialized tools for these functions that you can operate as Photoshop plugins, and (ii) once you scan these adjustments into the scanned file, they are "baked" - the workflow is not reversible without rescanning if for any reason you want to change settings, which can happen.
(3) I suggest you scan the media with some basic luminance and colour adjustments to get the photo looking about right in terms of avoiding clipping at the dark or light ends of the tonal range, not too contrasty (to preserve detail) and colour balance about right to avoid the need for very large adjustments in post-processing. Then open the scanned file into Photoshop and use Photokit Sharpener Pro 2 for sharpening - it has settings that were especially concocted for film and they work pretty well, with a lot of scope for customizing them. They work on their own layers, so you can change/discard as you see fit non-destructively, and also do selective sharpening. On a duplicate image layer below the sharpening layers, apply Neat Image for grain mitigation. Of all the noise mitigation programs out there, I have consistently found Neat Image to be really very good for dealing with film grain. Having this on a separate layer again preserves non-destructive workflow, allows you to dial-in or out (using layer opacity) as much or as little as you want and allows you to apply grain mitigation selectively in different areas of the image by using elementary layer masks. By playing between the grain mitigation and the sharpening layers, you will get the balance of smoothness and definition that makes the most sense for the photo at hand.
(4) If you are printing these photos, you would then use PhotoKit Sharpener Pro 2 again, but this time the output sharpener which is designed for printing (and other outputs) - this being a quite mechanical selection of the resolution and dimensions of the print - it does the rest. It builds on the initial sharpening discussed above (a.k.a. "Capture Sharpening").
I think this kind of workflow could give you the combination of quality, customization and non-destructiveness that you will find satisfying.