DDR5 hardly matters right now, nor does PCIe5.
Current DDR5 seems to be about 0-3% improvment for the vast majority of use cases. As DDR5 speed and timings improve, this should increase, but remember that the memory controller on Alder Lake is first gen and board makers will likely improve memory traces and timing training in future boards. If you are buying everything top end, of course go DDR5 - but otherwise the money spent on the DDR5 price premium would net better performance with going DDR4 and using that extra cash to step up the CPU, GPU, cooling, etc. to something better.
There is barely any advantage to PCIe 4.0x16 versus 3.0x16 for a gaming system, and that likely won't change much between 5.0 and 4.0. The extra bandwidth does open up possibilities for things like additional GPUs and NVMe drives for VM passthrough on consumer/gaming grade hardware, since x8/x8 Gen 5 will have the same bandwidth as x16/x16 Gen 4, but I think current mobos only wire the one PCIe slot for Gen 5 anyway.