My experience
Flew AirEuropa, BCN to PMI (Mallorca) after arriving in from ATL in D1. Was given lounge access due to J travel and then connecting onward. No lounge access in PMI departing to BCN as I was not heading back to US until the following day. Lots of conflicting info about lounge access as Skyteam Elite+ with 3rd party lounge in PMI. Note, I was on Air Europa stock, not DL.
I received ability to choose my seats at booking (roughly 5 months ahead of time), and was not charged extra. Received all Skyteam Elite Plus benefits, luggage allowance, SkyPriority checkin and boarding.
I did not receive ANY RDM or MQMs, however. Apparently, my seats were booked in N fare which is not eligible for any accrual. My biggest peeve with that, is Air Europa does not disclose any fare class you are buying.... simply $.