Geamon's right. Setting up one file for each format would be a pain and create bloat. In my packs I provide a map with grid, a map without grid, and then a maptool file with a few more bits addes - vision blocking, lights and so on.

The main issue is making sure that the grid in your map is an even number of pixels. So don't create it at 100px per grid and then downsize it by 33.3%. No-one can line up a grid to a 33.3px square. Some Vtts prefer pre-gridded maps. Others (like maptool) prefer them without.

Obviously leave off any secret information from the vtt map. In the vtt it's used as the board - so if it's there, the players will see it.

When you save out a jpg, use come compression. You can't see the difference between maximum and high (or even medium) quality inside the vtt. As people play with these over the internet, the filesize really matters. Hope that helps?

If you're going to do maptool files, then pick up the latest build and play around with it. That's the best way to figure out the questions that you need to ask about it.