I wrote a post on this a couple years ago. One difference is that, where this post is focused exclusively on impact, I also talked about some people wanting to gain career capital from volunteering or wanting a volunteer opportunity that helps you feel good and recharge.
https://forum.effectivealtruism.org/posts/ScLHyCY6JCr5FtuiY/effective-volunteering
I wrote a post on this a couple years ago. One difference is that, where this post is focused exclusively on impact, I also talked about some people wanting to gain career capital from volunteering or wanting a volunteer opportunity that helps you feel good and recharge. https://forum.effectivealtruism.org/posts/ScLHyCY6JCr5FtuiY/effective-volunteering