- You can use a device configuration profile for this. See https://oofhours.com/2020/04/07/outlook-and-azure-ad-join-automatically-configuring-the-users-mailbox/
2a. You can use OneDrive files on demand so that the links to the files appear, but they are only downloaded when a user opens them. Those settings are contained in the ADMX above.
b. I haven't seen those settings.
- You can create a custom OMA-URI profile for the timezone. See https://oofhours.com/2019/12/20/configuring-time-zones-part-1/ as for language packs, there are multiple ways. This is one way https://www.anoopcnair.com/intune-learn-to-deploy-windows-10-language-pack-step-by-step-mem/
- I believe that the policies will stay, unless you deploy a new policy with different settings.I haven't tested this in a while though.