pci-e 4.0

Right so TLDR, building my first rig since a 2008 era q66 stepping 1st gen quad core... I've had mac's since but all are circa 2008-2012 retrofitted with sata3 ssd's... This will be my first 'modern' pc with a m.2... I've got a B550m pci-e 4.0 m.2 motherboard... Now I was going to splash out...