NVMe upgrade on a PCIe 3.0 motherboard: 4.0 vs 3.0 performance and OS cloning

[MarkYM]

I'm planning to upgrade my older gaming PC with a new NVMe SSD to improve load times and overall system responsiveness. My motherboard has an M.2 slot that supports PCIe 3.0, and I'm trying to decide between a higher-end PCIe 4.0 drive that would be future-proofed or a more affordable PCIe 3.0 model. What's the real-world performance difference for gaming and general use, and are there any specific steps or tools I need for cloning my existing Windows installation from the SATA drive to the new NVMe drive without having to do a clean install?