Z690 motherboards will support both DDR4 and DDR5 memory

DDR4 sticks won't fit in DDR5 slots either So, if you're planning to keep your current motherboard, sticking with DDR4 is the way to go 5

In this short video, I will explain how to check whether your motherboard supports DDR5 RAM

ddr5 slot compatible with ddr4 DDR5 RAM Sticks Aren't Physically Compatible With DDR4 Slots Given the difference in voltage requirements and other crucial modules, DDR5 RAM

ddr5 in ddr4 slot No The sticks are physically different DDR4 wont fit in a DDR5 slot and vice versa