There's a difference between noise and grain, you will get more noise on colour negs scanning than slides.
Film would be printed optically, or high-end scanned for pros back in the day of film being mainstream for pro work.
If you want to isolate the grain, do a huge number of multi-pass scans and average them to remove the scan noise (vuescan can do this for you without extra interaction, or you can scan it over and over and stack the result in photoshop), the point here isn't scanning itself, but examing what part of that is actually grain, you can then make a judgement from there.
If still you want significantly finer grain at that point, you need to move up a format size to 645 for weddings, or try Portra 160 and Portra 400 which may work better for you (I found it has for me). Though if you plan on flatbed scanning MF, you will get less detail than your 35mm scans out of your coolscan sadly.
Then of course there is the issue of how well your lab is processing the film.
In any case, don't forget that viewing 100% crop is -MUCH- bigger enlargement than a print generally speaking. You're probably viewing it between 72 - 100 dpi on screen. So assuming 72 dpi (the standard figure), what you're looking at is what the grain would more or less look like in a 78x52 inch print viewing at a distance of approximately 50cm (same from monitor viewing distance). This simply isn't done.
When I got a 30x40" print done for a small gallery showing (matted to 30x36) viewing distance is approximately 1 metre to 1.5 metres for both myself and just about everybody looking at it.