Super helpful community. Tons of info available. Lots and lots of questions all ready answered and searchable.

https://grapheneos.org/

https://discuss.grapheneos.org/

If you mean the work profile:

1. The VPN does not apply to the work profile, i think the app that creates it needs to define a proxy or VPN, otherwise it's a direct connection.

2. I think you can't easily set up a VPN in the work profile, but I never tried it. If you used Instagram with a VPN up until this point, it might be good to continue using it. If you didn't, don't start now if you will stop using Instagram soon anyway.

3. You can "mount"/give permission to read specific folders of the main or work profile on the other one. It's read-only. For example WhatsApp has an option to switch the image selection to the main profile when sending an image.

Instagram bad. Get rid of it. Lol. My thought would be use it from a web browser.

1. 2. Every profile is its own unique sandboxed area supposedly. So if you decide to use a VPN each profile links to your VPN provider as its own new device. Thus having two connections with mullvad creates two separate devices for each profile. Running a VPN is always a better method to browse besides the security and privacy aspect. That being said. I would switch servers once your done with your own personal accounts for whatever apps you use which are each sandboxed BTW by default. Side profiles do not unless you select the setting run in the background. Consumes a lot of battery. But the main profile does. So switching back to owner from secondary profile your still connected to VPN inside owner. It doesn't drop the owner profile connection because owner is always running. Its the anchor for the OS IME.
2. I haven't found a reliable way to transfer photos other than flash drive with adapter or Bluetooth to PC then Bluetooth back. I'm all ears on this one. I've even text them to myself which for privacy is not a good option.

Edit account to profile. Doing to done.