PCIe SSD in PCIe lauffähig?

You're referring to NVME based M2 SSDs, correct? But yes if the SSD is PCIE spec then of course the speed will be less when used on PCIE

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m2 slot pc 2 supports both SATA and PCIe, an module may only be inserted in either one of the two interfaces, so check your motherboard documentation

m2 slot screw A PCIe SSD would not be any slower in a PCIe slot because its maximum speed is that of PCIe PCIe SSDs cannot go any faster than PCIe