While the Single editor certainly works, it's probably not your best bet for manipulating single photos. If you're going to use Photo Grid, better stick to multi-photo mashups.
Similar to the High editor, Wide outputs a photo strip, but horizontally. Here, we used it to get really creative and put the same photo in each panel.
If you enjoy coloring outside the lines, then the Free editor is probably for you. It drops the paneled templates and lets you tap and drag photos as you please.
One of the great things about Photo Grid is its ability to share and save files in either PNG or JPG format. What's more, the app lets you choose your preferred resolution.