What concrete things do I say, in a conversation with my manager to "set expectations"?
Do I say something like "I would like to ____ expectations this quarter, is it sufficient to complete project A & project B?"
What if I am new to the company, and unable to contribute meaningfully to a significant project, or there is downtime when no projects are available?
Can I say I'll fix some unknown volume of bugs this quarter?
This might be related to this question:
This depends a lot on your level and company - I recommend attaching those to questions around performance next time, especially as this question is fairly high-level.
Answering the question, I recommend the following resources:
Do I say something like "I would like to ____ expectations this quarter, is it sufficient to complete project A & project B?"
I think this is fine. To make it more granular, I would try to get some signal on:
What if I am new to the company, and unable to contribute meaningfully to a significant project, or there is downtime when no projects are available?
If you're a junior or mid-level engineer, I would ask other engineers on your team for work, especially senior+ ones.
If you're a senior engineer, the expectation is more around creating scope for yourself. Here's my in-depth advice on how to do that: "How do I come up with innovative, impactful ideas and bring them to my team?"
Can I say I'll fix some unknown volume of bugs this quarter?
I highly recommend against this. The amount of bugs a team has will vary a lot, and the bugs themselves are highly variable. Some bugs are 100x harder to solve than others - The depth of bugs fixed is more important than raw quantity.
is it sufficient to complete project A & project B?
I don't like this framing. This makes it sounds like you're asking for a checklist of what needs to get done for your career advancement. Instead, I'd frame it as "Here's what I think is important for the team, what do you think? Do these projects align with hitting this perf goal?"
Which company and level are you? What might be acceptable for a new grad may look very bad for a senior engineer.