The back buttons are mandatorh, and there’s a specific config someone made that I altered slightly for personal use, but I can’t remember the creator’s name. It was the highest used one at the time I downloaded it though. There’s definitely a small learning curve, but the reward is portable access to a great MMO!
Honestly I absolutely love the customizable nature of the Deck for individual programs, especially because I was able to pair 4 different build and equipment tabs to each of the face buttons so I can swap between all 3 elite specs for my engi main. I just wish they had official controller support with their UI like how I’ve seen FFXIV’s hotbar with multiple on-screen “pages” you can flip through easily.