You just gotta try those that you see on the Microstock Poll tab to the right, see what works for you. Nothing is particularly different from photos.  As for "shadiness", again, there isn't a site which haven't been complained about. Trial and error is the best way to go, thanks to massive uploads that can be done easily through all sorts of 3rd party software.

I have fair sales of vectors on Deposit Photos.  The problem I think with Canstock, is that, no matter how nice a jpg preview you include, they generate their own preview, and do it wrong.  So the vectors don't look good.  I only offer the jpgs on Canstock now.

This was a great problem when Vectorstock updated their previews to a higher resolution. Now I have a bunch of vectors
that look like crap...

If you want the preview to be without any surprises in sites that just take EPSs, or potentially regenerate their preview
(which could be anyone) I have 2 tips for you:

1) Work your vectors in sRGB (you wont have any hustle from any site about the color mode)
2) Always have a white filled Background layer (no outline) in your Artboard dimensions
 
EPS to JPEG prices on Canstock have a huge difference so I suggest you convert all your EPSs in RGB and reupload.

Hello,
I've tried two agencies that in my experience are worth uploading:
- Sign elements : I make an average of $70/$80 there and had two times this year a month with 200$ (probably some extra licence...)
- Photospin : average of 50$/month

You can also try vectorstock, slow earnings but constant. $360 a year is not bad for me, when you add it to the other earnings

As always it depends on your niche, volume, talent etc...