Following up a bit on my own question. It seems that you can only have two keys per Primary App ID. From this doc: https://help.apple.com/developer-account/?lang=en#/dev77c875b7e it indicates that the reason for the limit of two is that the idea is that if the single key is compromised then you generate an new one (the second key) and update whatever uses it, then you revoke the original key.
As for servicesIDs it seems you can have multiple, eg; one per environment, but I'm unsure if that is needed, and they'd all use the same single key.
sharkusmarkus
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Developer System Status page has been updated to indicate there are performance issues with App Store Connect and App Store Connect API
https://developer.apple.com/system-status/
Seems like developer status page has now been updated to indicate performance issues with ASC and ASCAPI.