Yes, you can install a 1x PCIe card into a 16x or 4x PCIe slot

Make a PCIe 1x Slot Compatible with Longer Cards Linus Tech Tips can you put pcie 4x in 16x slot I have a pc setup i7 10th gen cpu in an asrock b460 This mb support in 1st pcie 16x, in 2nd pcie slot only 2x and it also has 2 pci-e 1x I have a candy jar clusters slot you can DIY your PC in no time, quick and easy PCIe EZ-Latch Unlock the latch of the PCIe slot easily when remove the graphics card in the PCIe slot EZ-

can you play slot machines at 18 It should work just fine The port should automatically drop down to x4 You may need to get a smaller plate though