i heard from a friend of mine that sd cards bigger than 32gb are pretty slow on downloading stuff online, and also when booting ur 3ds with it on. it doesnt rlly affect overall performance tho, but more so something that may get pretty annoying to deal with.

128gb sd loading times on the o3ds are brutal tbh, 64 is ok and 32 is probs way more than enough if youre barely hitting 4gb rn mostly depends if you want to have a lot of games at once though

of course if you want a lot of games for sure you can go to 256gb , 512gb and even 1 tb for many games

i think thats extremely overkill tbh, i use 128 and its mega comfy though i guess you could do 1 tb if you wanted the entire 3ds catalog for whatever reason but load times would be legitimately insane id imagine

i use a 64 gb. load times are... okay. sdxc works as long as you format it to fat32/MSDOS via rufus or something