Allow guests to see each other and access my local network separately

Yep, this functionality was there in the past and needs to be added back.

There's a more detailed discussion about it here:

https://community.netgear.com/t5/Idea-Exchange-For-Home/R8000-Guest-Network-Needs-Separated-Wireless-Isolation-and-Local/idi-p/1050376/page/3#comments