A 64GB SD card is $4 and should fit the majority of games that fit the "no DRM" requirement. This product is not for me but i would just standardize on 64GB cards. Should be big and fast enough for most example games they show.
For the full old school console experience you shouldn't have hundreds of games lying around anyway, most people had less than a dozen games per console.
Where I live no 64GB SD card is 4$ and more like 8$-12$ and the quality of those is shit.
Even if they were 4$ I would still see it as an absolute waste of money and storage. You _will_ have a better gaming experience using a cheap nvme/ssd. Like I said for games that would require a 64GB SD card sd-speed is too slow.
For the full old school console experience you should use a console and not emulate the nostalgia (oh and this doesn't feel nostalgic to me at all)
> most people had less than a dozen games per console.
This isn't a console and if you want to for instance emulate every of the dozen games per console you would for 10 consoles still need 120 SD cards at the price you listed this would add up to 480$ for that price you could buy one fast and reliable nvme that would fit your needs...