I remember reading that Lennon was influenced by Fleetwood mac for Sun King, literally that song you mentioned so decided to pipe in here for the hell of it. I checked wiki and Harrison confirmed it on there, so I guess the Fleetwood mac song did come first.

”” In an interview in 1987, Harrison said that the recording was inspired by Fleetwood Mac’s “Albatross”. “At the time, ‘Albatross’ (by Fleetwood Mac) was out, with all the reverb on guitar. So we said, ‘Let’s be Fleetwood Mac doing Albatross, just to get going.’ It never really sounded like Fleetwood Mac… but that was the point of origin.”