Autonomous Transaction Processing comes with predefined CPU/IO shares assigned to different consumer groups. You can modify these predefined CPU/IO shares if your workload requires different CPU/IO resource allocations.
By default, the CPU/IO shares assigned to the consumer groups TPURGENT, TP, HIGH, MEDIUM, and LOW are 12, 8, 4, 2, and 1, respectively. The shares determine how much CPU/IO resources a consumer group can use with respect to the other consumer groups. With the default settings the consumer group TPURGENT will be able to use 12 times more CPU/IO resources compared to LOW, when needed. The consumer group TP will be able to use 4 times more CPU/IO resources compared to MEDIUM, when needed.

Explanation
https://docs.cloud.oracle.com/en-us/iaas/Content/Resources/Assets/whitepapers/deploying-custom-os-images.pdf A template of a virtual hard drive that determines the operating system and other software for an instance. For details about Oracle Cloud Infrastructure platform images, see Oracle-Provided Images. You can also launch instances from:
Trusted third-party images published by Oracle partners from the Partner Image catalog. For more information about partner images, see Overview of Marketplace and Working with Listings.
Pre-built Oracle enterprise images and solutions enabled for Oracle Cloud Infrastructure Custom images, including bring your own image scenarios.
Boot Volumes.
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Explanation
https://docs.cloud.oracle.com/iaas/Content/Object/Tasks/usingpreauthenticatedrequests.htm You can create an unlimited number of pre-authenticated requests.
You can't edit a pre-authenticated request. If you want to change user access options in response to changing requirements, you must create a new preauthenticated request.
URL: https://docs.cloud.oracle.com/iaas/Content/Object/Tasks/managingbuckets.htm You can change a bucket's access from public to private or from private to public. Changing the type of access doesn't affect existing pre-authenticated requests. Existing pre-authenticated requests still work.

Explanation
References: https://docs.cloud.oracle.com/en-us/iaas/Content/Network/Concepts/fastconnectoverview.htm You use a DRG when connecting your existing on-premises network to your virtual cloud network (VCN) with one (or both) of these:
IPSec VPN
Oracle Cloud Infrastructure FastConnect
You also use a DRG when peering a VCN with a VCN in a different region:
Remote VCN Peering (Across Regions)

You can scale up/down your Autonomous Database to scale both in terms of compute (CPU) and storage only when needed, allows people to pay per use.
Oracle allows you to scale compute and storage independently, no need to do it together. these scaling activities fully online (no downtime required) in Details page Autonomous Database in OCI console, click Scale Up/Down. Click on arrow to select a value for CPU Core Count or Storage (TB).
Or Select auto scaling to allow the system to automatically use up to three times more CPU and IO resources to meet workload demand, compared to the database operating with auto scaling disabled.