Is an ASROCK X570 TAICHI necessary for you? Since you are only going only going with a decent GPU, those SLI and PCIe 4.0 bandwidth /features may not be required. Since you don't want to overclock the 3900X then mobo may not be worth it, but you could just get a cheaper one. Since its the X570 chipset, I'd guess all Motherboards with that chipset would be high end and packed full of features anyway...
However, I cannot check is there is a cheaper motherboard with the X570 chipset, as I don't live in Egypt..
With the saved budget you could invest in a better GPU, especially since, when/if you do game on that PC, then your PC could do more with a better GPU, and it would be better matched to the amazing CPU you have.