My approach: It depends. These examples below are what I do most often, but are not exhaustive.
For a standup, I want to include details that were particularly frustrating so I can find out if I need to keep hacking away, identify someone to help, or have someone tell me to give up.
When I find stuff while testing a user story, I’ll chat the developer directly. Usually it’s something simple (a missing constant, the wrong branch) that’s quickly resolved. Bigger questions that need more input move to the team channel or a video call. If you find something small and weird but unrelated, give your team the gift of starting your message with [not urgent] and a description of what your current context is since they’re probably context-switching. (Bonus points if you get them to pair or do nothing during testing so they’re not switching contexts.)
For a closing comment on a user story, I want to describe what I did well enough for me or someone else on my team to replicate it. Often I’ll start writing the report mid-way through the testing to discover what I forgot to test.
Number of test cases people: I haven’t worked in a context like this. I’m curious if the people asking think that all test cases are the same complexity, or why they’re asking. Dig into what they’re worried about to figure out what needs you should be addressing.