Bonvoy (Marriott) Gold is not a high tier. It only requires 25 nights per year (15 of which can come from having a Marriott affiliated credit card) and doesn't give lounge access or breakfast. Bonvoy tiers in increasing order are Silver, Gold, Platinum, Titanium, and Ambassador (at 100 nights and $23,000 spend).

OTOH Hilton Diamond is a top tier, IIRC 75 nights or a premium Hilton-affiliated credit card, It gives lounge access or breakfast and possibly upgrades or late checkouts if available,

I suspect the lounge access is only applicable when flying the airline that operates the lounge.

Note that this should not be confused with SkyTeam ElitePlus status.