there is no linking of accounts. you have to wire funds or crypto into your account. im not sure but bitstamp may not offer credit card buys any more. if u wire funds in, u can buy xrp directly. with the cc option, u can only buy btc, sell it, then buy xrp.

wallets are a whole other topic. some prefer nano s others prefer different. some keep it on the exchange. but yes, u transfer and later if you want to exchange it for dollars, u deposit it back into your account then u can request a withdrawal in USD or even in XRP in the form of a wire or even onto a debit card.

im not an expert in wallets. again, xrp chat hass tutorials on this.