Render a content type bundle in a custom module template
I'm not sure what you're exactly asking, but there are various modules that allow you to display entity forms in a block, for example Entityform block (Disclaimer, maintained by me).

Either use that, you can use form modes and/or form alters to then customize the form, or just look at the code to see how to do it.

One thing that this module doesn't support yet is editing existing entities, I'd love to add support for that using the plugin context system.