Dear Writer with Many Hats…
One agent isn’t likely. Literary agents know their markets deeply and foster relationships with many editors—which is a lot of work. Add knowing the entertainment industry and its markets, too, and networking its pool of professionals, and we’re talking Herculean workload. But you don’t necessarily need three separate agents, either. Quite a few lit agents rep both YA and some category of books for adults, so put your first efforts into researching a lit agent who reps YA and memoir. That agent will almost certainly have a relationship with a subagent who handles book-to-film rights and maybe original screenplays. In that scenario, when the subagent sells your screenplay, you’ll get your full share of advance and royalties while the agent portion is split between the two agents. And hey, if the agent/subagent scenario doesn’t work out, don’t feel overwhelmed by the thought of three. I have three agents. My first agent repped children’s books only, so when I wrote Writing Young Adult Fiction For Dummies and then Writing New Adult Fiction, agents specializing in adult nonfiction and craft books came into the mix. Everyone has their lanes and it’s all good. Just remember, whether you use one, two, or three, your representative(s) should have a strong market knowledge and professional network.