There’s no specific arrivals lounge outside of security at Schiphol other than a Regis Express lounge / office etc. near the train station. And for oneworld access to work for oneworld lounges, you must be departing on a oneworld flight.

There are two Aspire lounges (T1, T3) accessible via Priority Pass and pay, iirc. The T3 lounge offers showers. The listings also state “Maximum 3 hour stay prior to flight departures“, so you might not be granted access.