If you're wondering what model to get, if you can use a screwdriver and follow simple instructions you can purchase the 64gb model and then get a 256gb NVME ssd(Samsung pm991) for ~35 off amazon. Takes only a couple minutes to remove/install the drive. Takes longer to reinstall steamOS to your device.
I did this in March when the first steamdeck sale happened. Haven't had a single issue with my ssd - other than the updater saying my ssd needs a firmware update but fails on the install.
Don't use a cheap no-name brand(Onn, etc) USB stick for your steamOS recovery image. I tried several and they all would claim install success but the OS would get stuck in a boot loop in the reboot after "successful installation".
I ended up buying a cheap Sandisk and it worked like a charm. I also got an anti-glare screen protector which does wonders for outdoor gaming.