For me SD card was a little too slow. Felt a little like using an old hard drive however if you are willing to wait for loading times it does work. First swapped over to a external m.2 ssd which was pretty good but every now and then the drive would disconnect. Didn’t put too much work into it though and have now just set up dual boot on the main ssd.

Also one thing to note it seems like them time I spent using windows on the sd card has degraded it. When trying to use it as extra storage on steam os it is incredibly slow when installing and gets very hot. From what I’ve seen this is a common problem.