Yes, I've been using it with rtx 3080 for a year now.

I have it in operation with an MSI ventus 3x, works.

Depending on the model, yes (there are filters for the length here, you have to research the height and thickness of the card yourself):

Max. internal dimensions:
Length : 12.99"/ 330 mm
Height* : 6.29" / 160 mm
Width : 2.24" / 57 mm

Here is the manufacturer's page (pictured again):
https://www.razer.com/de-de...