the thermal paste will not be needed for a while at least, the cooler will ship with paste ready to apply.
you can see it here.
the RAM should be the same kit. larger modules of faster speed can be had. the WD velociraptor is a great drive but even cheapo SSD's can dwarf its performance. the intel 660p is cheaper and faster than both the drives you selected, I would install the OS to the intel drive.
results for general idea only. your mileage will vary. https://ssd.userbenchmark.com/Compare/Intel-660p-NVMe-PCIe-M2-1TB-vs-Samsung-860-Evo-1TB/m602553vsm423831
the AX is a top notch unit and you cannot go wrong with the choice but the price is a dealbreaker for me, the seasonic focus platinum 850W unit has more than enough wattage even if you chose to OC and is a top notch unit too.
the performance should be slightly better with the faster storage and RAM a bit cheaper to boot.