Top modded Rust servers

It varies. Some wipe weekly, some monthly, some only when Facepunch forces a wipe on the first Thursday of the month. The Next wipe column gives an estimate based on past behaviour, but the server's own page has exact dates and wipe history.

Many sell kits, privileges or queue skip for real money, but that doesn't automatically make them pay-to-win. It depends on what's sold. Some servers only sell cosmetics; others sell powerful items. Check the server's description or store before you commit.

Vanilla servers run the game exactly as Facepunch made it: 1x gather rates, no kits, no teleports. Modded servers change the rules, usually with plugins. That can mean higher gather rates, custom loot, events or entire game modes. If a server changes gameplay, it must be listed as modded.

Yes. Mods run on the server side, so you don't need to download anything extra. Just join like any other server. The only exception is if the server uses a custom map or mods that require client-side files, but those are rare.