Out of those, application performance class is the one you want. Even better is a real-world random read benchmark.

• The capacity standard isn’t super helpful. Everything from 64GB to 2TB is SDXC, which is supported.
• The Steam Deck only uses UHS-I. It’ll work with UHS-II and UHS-III cards, but they won’t have any meaningful benefits.
• Pretty much any decent microSD Card in 2023 is class 10. If it’s anything else, that’s a red flag.
• Higher UHS speed class and video speed class are probably better, but they’re measuring write performance. For playing games, random read performance is far more important.