This is a pretty good set of relays.

You can maybe add wss://relay.nostr.wine

for reading (to write to it, you'll have to subscribe as it's a paid relay, but many find it useful and subscribe).

Absolutely not -- it's for everyone.

The dev(s) are Japanese, so some design choices are made basis Japanese aesthetics.

It's neat and not too cluttered & I like it, but as far as I know, not many non-Japanese use it. But maybe they do now 😁