Hello,
I've been an SCBWI member since 2019. I echo everyone's thoughts here that it definitely is worth being a member. You can always try it out for a year and see if you like it. But often it takes multiple conferences/events/participation etc to gain info or get direct benefits/ recognition through it.
If you have a local chapter, I would definitely participate in those. A smaller community will help you network more and find peers and critique group members to grow and share your journey with. I'm from India and the chapter here isn't very active or happens in cities where I'm not available. So I gained most from the online conferences.
SCBWI has monthly drawing challenge and as you mentioned the submission for bulletin etc. I've had a couple of my work selected for the bulletin. I usually just edit existing artwork that I have based on their submission requirements so that I'm not spending too much time on it. If they choose it, great! Their "Book" has handy info about latest in the market and details for agent and publisher submissions, portfolio tips etc.
The conference can be a little pricy but think of it as a return on investment. Though the conference this time in Feb is in-personas well as virtual, the online event doesn't have the usual portfolio showcase as it's reserved for the in-person conference only. I had won the first virtual portfolio showcase in 2020 and that helped me get a book deal from a top 5 publisher. I got 3 interviews with art directors and as of last month, one of them got converted to another book deal. So there are definitely benefits. SCBWI also commission portfolio winners for creating the conference banners/book cover/website illustrations etc. They also asked me to create a short video for helping promote their conference this time. It's a good platform and opportunity to get recognition.
Best of luck!