that is fantastic:
http://www.bhphotovideo.com/bnh/controller/home?A=search&Q=&b=999&a=0&shs=&ci=1151&ac=&Submit.x=11&Submit.y=9It scans beautifully, and has presets for film types. The good news about Pacific Image, Nikon, Agfa and a few others is that they spent the money on developing drivers that are optimized for professional output. Mechanically and optically, a scanner is simple but the software that understands gamma, adjacency, and other film stuff that Kodak and others have researched for years isn't so simple. Side-by-side, you can easily tell the difference between scans on these machines and the cheap do-it-all scanners.
The problem with film scanners is that you still have to do one at a time unless you get a motorized one for bigger bucks. They are set up to do it more easily, though, without having to deal with that lid and cutting the film the way my HP scanner with the film adapter does.
As far as resolution goes, that gets complicated. Hi-res scans do take longer and the files are huge, but the results are startlingly good. Much of the info will be lost on 5x7's though, so it's best to experiment with the results on each printer you might use.
The easy answer is to not scan everything, or at least not scan them right away.
Properly stored, modern color film and negs will last at least 50 years, maybe a hundred. I've got chromes from back in the 60s that still look good, and most were stored in hellish conditions.
On edit... rereading the original post, I don't understand why grain should be a problem with EI 100 film. I've done scans of EI 1000 film at hi-res with few problems. Maybe it goes back to the driver and how the interpolation works.