I have a build arriving soon, Ryzen 5 3600x, b450 tomahawk and RX 5700 xt. The memory, 2x8GB ddr4 will be arriving a couple weeks later. Using a previous 8GB PC3 from an older build in the new machine, will I experience harsh bottlenecking? Or should I just wait the couple weeks to avoid complications? Anyone have any experience with a similar scenario? Thanks!