It's been a bit since I've been in 4-H, but once my child is old enough, I'll be starting her in a club.
I was in 4-H from 8 to 18. I did mainly horses, but many clubs (like mine) encourage kids to explore other things - crafts, creative writing, other livestock etc. Our group did a LOT of volunteer work as well, and some minor fundraising (craft shows etc), to fund the volunteer opportunities.
Since we did horses, we had 4-H horse shows available every few weeks. I think my club met once a month. The "big show" was the County Fair, and we usually stayed at the fairgrounds for the whole week. I personally showed horses, dogs, and entered items in baking, art, photography, creative writing, and more I've forgotten.
I never did Girl Scouts, but I would imaging it's probably somewhere in the middle of how Girl/Boy Scouts is, and how FFA (Future Farmers of America) is. FFA (at least my club) is more heavily involved with agriculture than 4H, though 4H does do some ag, it doesn't seem as much as FFA (but it could have just been the clubs I was in. For instance, in FFA, we did raise poultry as a club and did take it to the slaughterhouse as a "field trip". This is more common with FFA I think that 4H.
I loved both FFA and 4H - they are exceptional programs for youth to learn how to be reliable and creative, and the people who are leaders (that I knew) seemed dedicated to their clubs and making sure it was a good program for all. I know in my club, the leaders participated in meetings, but the meeting were ran by 4 club members, elected by the club members. I served as Secretary for my club for a few years. The volunteer work was wonderful and fun, and I look back and can actually say I did good and made a difference in the lives of others, due to 4H.