I have the same stutter but I narrowed it down to the Atmosphere tick box in the Show menu of the editor. If Atmosphere is unticked the scene runs smooth at 40fps. With Atmosphere ticked it alternates between 10 and 30 fps about twice a second.
EDIT: after further investigation it is the real time capture of the skylight in the sun and sky actor causing it. I have not a lot of memory though with 6 GB and a RTX 3060 laptop gpu