TLDR: macOS virtualization is as fast as native due to hypervisor support, with free but limited driver support thanks to virtio. MacOS guests are limited to 2 at a time, and cannot use iCloud services or log in to the App Store.

Also FYI:

- launch times are fast enough for serverless

- you can restore snapshots for macOS guests but not for Linux

- Apple's open-source container support is built on Virtualization, making it a much more secure option than Docker

What's needs investigating is access to the secure enclave. You can login with an apple ID and use enclave API's; it's not clear if this is emulated or handled using the host enclave with a different scope - i.e., if this presents any security issues. To be conservative, one might avoid logging in using an Apple ID with sensitive information in an automated/CI context.