Note: Shader caches and proton prefixes/compatdata will still automatically go onto your internal drive even if the rest of the game is on SD card, for performance reasons. This is mostly a problem with the 64gb LCD Decks, which is why the advice with those is always to open them up and put in a 1 or 2tb internal drive. (2230 single sided nvme. I use the MP600 mini by Corsair.)
Im new to the Steam deck world, simple question, can the micro sd be used to store full games?
Yes. Especially for the lower capacity ones, SD card is your primary form of mass storage.
Yup.
Note: Shader caches and proton prefixes/compatdata will still automatically go onto your internal drive even if the rest of the game is on SD card, for performance reasons. This is mostly a problem with the 64gb LCD Decks, which is why the advice with those is always to open them up and put in a 1 or 2tb internal drive. (2230 single sided nvme. I use the MP600 mini by Corsair.)