Coil whines can come also from graphics cards, but it starting later and not instantly with graphics card change certainly hints also other factors being in play.
(remember if there was some driver update at that time?)
With that graphics card being very moderate in power consumption load isn't that much...
But are you heavy PC user with lots of power on hours (including gaming) for PC?
Only 730W Be Quiets I've seen in reviews have been standard cheap PSUs and something I wouldn't recommend to any enthusiast or higher end gaming PC.
With that wire spaghetti those cheap secondary capacitors don't even get any real cooling airflow:
https://www.techpowerup.com/reviews/beQuiet/PurePower_L8_730W/4.html
So PSU moving on toward its design goal (of failing) is possiblity.
Be Quiet has absolutely nothing going on for its PSUs.
Lots of them are seriously expensive for design/performance/component quality.
Seasonic Focus Plus is where top performance/quality meets price.
https://www.overclockers.co.uk/seas...plus-gold-modular-power-supply-ca-05q-ss.html
For that power consumption level graphics card and stock CPU 550W would be also enough.
But 650W gives good reserve for some higher consumption graphics card.
Antec EarthWatts Gold Pro has same insides with semi-modular cabling.
https://www.overclockers.co.uk/search?sSearch=antec+earthwatts
And for lower budget I would keep Bitfenix Formula as minimum.
https://www.overclockers.co.uk/search?sSearch=bitfenix+formula