I also liked your slides, and appreciate you sharing them with us.
As an active member of both LibriVox (LV) and Distributed Proofreaders (DP), I can share my perspective of DP with you and hope it is helpful. I've been a member of DP for over 6 years, and have worked in just about every activity possible there. Yes there are a large number of different activities available, but a member can just concentrate on just one (or more), depending on their likes and dislikes. So my first recommendation is not to let the variety of different activities overwhelm you; just take it slow and at your own pace.
Compared to LV, DP is
more structured, with a greater learning curve than LV, but it needs to be. DP's concept of quality ebooks is stronger than that of LV's audiobooks. In DP we are transcribing the written word; so the content must reflect the original as accurately as possible. LV's focus is an audio version of the ebook, which may not necessarily follow the ebook exactly (except with the Word Perfect standard). As a result DP, has more guidelines to learn and follow in order to create a standardized proofing and formatting of ebook pages, so that the post-processor (PP - the one who assembles the individual pages into the final ebook) has standardized output to work with, from project to project.
When I first began proofreading, then formatting, at DP, some of the guidelines didn't make sense to me, and I thought some were unnecessary or useless. It wasn't until I gained more experience and began PPing projects that I understood the "why" of the guidelines: for example, why some guidelines had strict requirements and why some were silent.
DP is not for everyone. But if you are detail-oriented, willing to put in the effort, like the teamwork spirit, and don't have any preconceived ideas of how DP should work, I think you'll find DP an enjoyable place to spend some time. You'll find those at DP extremely helpful and friendly.
For full disclosure, in addition to the numerous other activities I enjoy at DP, I'm currently also an admin there, working on fixing broken projects (projects with missing pages and other issues).
If you decide to join there, say hi (same ID as here)