The old R4 (and 1.1 clone) are limited to now-SDHC cards. So you are basically limited to ≥2GB microSD cards.
So it really boils down to what roms you put on it. You can also make a bit more room trimming the ROMs with either the builtin ROM trimmer for Wood R4 or using this tool https://gbatemp.net/threads/ndstokyotrim-batch-trimmer-with-wifi-detection.55162/
R4 (and the 1.1 clone,) will work on any DS Lite or Phat without hassle. It will not work on the DSi(XL)