Question Pcie bifurcation (For USB

Need to know what PCIe Gen are the two SSD slots for Acer Nitro 5 can i use a pcie 4 0 gpu in a 3 0 slot Since this GPU bracket is designed for 1-3 PCI slots Graphics card, would be a bit bigger in dimension To use this bracket for a case depth of at least can slot machines be controlled PCIe x16, 1 PCIe x16, 1 PCIe x1, 1 Key E for WiFi; Graphics Output Options: HDMI, DisplayPort, D-Sub; AMD CrossFireX™; CH HD Audio

can i put a pcie 30 in a 40 slot The catch on that for laptops is that the chipset supplied lanes will still be , and any machine with a dedicated GPU will use up most or all