Capacity or technology? Depends what note types you’re storing and if you’re running a #wot #relay with a wide web or if it’s just for your own notes like #haven or a general purpose public node. If it’s public, RAM is most important.
Discussion
I should have specified haha, I mean a personal node.
If it's just for your own notes I would recommend running citrine locally. Although if you want to connect to the same personap relay on all devices you could use strfry, grain, nostr-rs or any others. Storage won't be a problem at all of you're just storing your own notes. A few megabytes.