PCIe 4.0 won't matter for another few generations unless you're in an enterprise or academic research application. It definitely won't matter for consumer gaming GPU.
+1, and same goes for storage if you don't do content creation or other data-intensive work, there won't be much benefit, though down the road there may be some scenarios that can take advantage of the full 5GB/s speed.
Currently for gaming the Samsung 970 Pro SSD is the fastest game launch drive. This makes it clear that there isn't much of an advantage to getting a Gen 4 SSD if you already have a fast Gen 3 SSD.
Personally I'm fine with the fact Asus did not add 4.0 support to Z490 motherboards, as I prefer not to pay $800 dollars for a motherboard, give me 3.0 and charge $499.99 and I'm good to go.