There's not much more I can say, that I didn't already say.
As Lazur suggested, you could probably re-save each file as Plain SVG, and reduce the size by a small amount. I'm still not sure what Optimized SVG is, but I'd be glad to try it, if you could provide a couple of test files.
Other than that, the only way to reduce the file size, is to draw the image with different type of objects or features. Like for example, if an image uses a lot of filters (filters typically provide fancy, 3d-like effects) they could be replace with regular solid fills, and cut the file size that way. Of course, that will change the appearance of the image. Or if there are imported raster images in the file, or other hidden contents, those could be removed.
But for the other files that I've seen, there's absolutely nothing in them that can be changed. Typically when artists provide these files, they've already made the files as small as possible. I suppose it's possible you might find one here and there with a lot of excess data, but I don't think it would be very common.
This is the best I can do, to come up with some kind of "process".
-- open the file
-- File menu > Clean Up Document
-- Watch the status bar as you click that, so you can see how much data was removed. Most of the time I expect it will say "removed 1 def" (which would probably remove less than 1 kb).
-- Save as Plain SVG (might remove 10 to 15 kb, I'm guessing)
As for recreating the image with different elements, we'd have to look at the files. Or you could learn more about using Inkscape, and be able to do it yourself.
Oh wow! I tried Optimized SVG. There's actually a dialog where you can pick and choose which data you want to keep or not. I managed to take a 96 kb file down to 21 kb !! I don't see any major changes in the appearance of the image. I'll make some screenshots of the settings I used in the dialog. Be right back.