Check your render settings. Any PBR needs lots of samples in order to get rid of noise/fireflies. If I want to get "clean," I set to a minimum of 15–20 pixel samples. Really good quality will be more, but that should be sufficient to get rid of artifacts in most situations.

As for whether Superfly is using your GPU ... assuming you have an Nvidia card, you have to set that in your preferences; otherwise, it will be doing CPU renders only by default. (Be aware too that the tech is such that GPU rendering isn't as capable as CPU in some aspects of quality.)

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Hardware: AMD Ryzen 9 3900X/MSI MAG570 Tomahawk X570/Zotac Geforce GTX 1650 Super 4GB/32GB OLOy RAM

Software: Windows 10 Professional/Poser Pro 11/Photoshop/Postworkshop 3