We are getting ready to implement Portal here. Our vision was to have it on our intranet in order to have only city staff be able to access data and maps. We want to use windows credentials to have Portal authenticate users and prevent multiple logins for users, essentially a better sign on experience especially for secure services.
Our consultant says if we do that then any GPS data collected with Field Maps will require the user to be on a VPN in order to upload back to the data store. He also said we will still have to maintain our cloud based AGOL account for our public facing apps and that employees will staff have to login. 2 questions…1) Does a secure wifi connection count for Portal to authenticate the user as being inside the intranet? 2) Is there anyway to install Portal to be the way we want but also still pick and choose the public side such as using Hub?
I have attached a diagram of our current ArcGIS Server setup.

Any suggestion would be greatly appreciated!