While Spellbreak is a cross-platform game, there are some things to note about which parts of the game are shared across platforms and which are not.
All level progress, earned Gold (from quests/level ups, etc.), and cosmetics will 100% carry over. All platforms are linked to a Spellbreak ID to enable cross-play and cross-progression.
The only thing that would not carry over is Purchased Gold. This is only usable on the platform from which it was purchased. For example, if you bought a Gold pack from the Nintendo Store, that gold would not appear when you login on the Steam version of Spellbreak. This is due to separate agreements across each platform regarding the purchase of in-game currency.
However, if you use that platform-specific gold to purchase an outfit, that outfit would appear on any platform you login from.