Hey there 
Is there a (relatively simple) way to make a public view editable?
We have just released an RBAC (role based access control) feature for Baserow that allows you to define more specific roles for users and in the next iteration will probably also allow you to define permissions on a per-table level.
That should roughly mimic what you are trying to do, except that the user editing would need to be part of your workspace, and not just have a link that they can click on.
And is there a way to apply filters from the public view URL?
I assume you mean filters that aren’t applied to your internal view but are applied to the external view but not by the external viewer themselves but by the owner of the view and therefore not reversible by the viewer?
That does not exist at the moment, a viewer can add their own temporary filters and you can filter on your view before you share it, there isn’t such a thing as a “per shared view filter”.