I am not able to grand guest the access to a webform. its possible to change access to f.e basic page.
Its possible to grant edit access but not view.

Grants on the node/xx/access:
View any webform content: guest /authenticated user
View own webform content: guest//authenticated user

installed modules:
Block Access 7.x-1.0
Content Access 7.x-1.2-beta2
Content Access Rules Integrations 7.x-1.2-beta2
Domain Access

I do not know why but the way to grant access is:
node -> webform--> form setting Submission access:

"These permissions affect which roles can submit this webform."

The the basic page access is to be set with webform -> access control, but not the form itself