Yep, that’s lumen for you. The devs get into the limitations a lot on their various livestreams, but the TLDR of good lumen behavior is this:
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You basically need hardware RT unless you want to be messing with a lot of per-mesh settings to get good GI. You literally need HWRT to get good reflections.
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Use analytical light sources next to dim emissives wherever you can if you want the look of emissives with stable lighting. If you do use emissive area lighting, make sure to make the emissive surface as big as you can and reasonably dim. Small, bright emissives will throw noise everywhere and it’s simply unavoidable, no matter how high you scale.
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If you absolutely need good quality, then go into the PPV and crank the lumen scene lighting quality and final gather quality as high as it will go. It will do a lot to make noise better at a massive GPU cost.
By the way, you say you’re just looking for good looking GI from static lights. If that’s the case, why not use lightmass?