Feedback requested on utility with event-level reports' privacy params

[csharrison]

The privacy of event-level reports are parametrized primarily by three factors:

• How many attribution reports can be generated by an ad impression
• How many bits of metadata attribution reports can embed
• How many distinct reporting windows are available. Note that more windows allows for shorter delays in the API if conversions occur in early windows.

We’re looking into whether our current parametrization makes sense, so we’re looking for information about:

• Which of these aspects are most important to you (e.g. you’d trade off bits of metadata with more reporting windows, or a stack ranking of these dimensions)
• Example parameterizations which would satisfy your critical MVP use-cases

Note that we're open to feedback about both the CTC and VTC use-cases / params.