<< I can't get one form to show right now.
From a user's perspective I can say the the form plugin does work.
It's been a while since I've looked at the documentation but I recall that , at the time, it was a bit confusing. Actually, getting an example form to show up on a page is pretty straightforward once you realize that all the form display and processing is generated in the yaml frontmatter of your form.md page.
Copy all the code here and paste it into a blank fom.md page. You should see a simple form on the front-end. Any text you add below the yaml stuff will display above the form. Hopefully, this will get you beyond square one so you can develop your own form.
Regarding multiple forms on a single page... using the conventional technique I don't see how this is possible as only one form can be referenced in the yaml area. Howeve r, a thought is that perhaps you can build forms as individual modules and combine those into one page? Not that familiar with Grav modules but that is how we'd approach it with Joomla.