Memory selection

SPEED
The STRIX Z690 can have DDR5 memory strips running at 4800MHz as standard speed, but can also have the memory overclocked by 200MHz increments up to 6400MHz. This is useful not just for overclocking but also to accommodate faster DDR5 strips.
However, the processor also sets a limit to the range of memory speeds: our choice, the intel 13500, is meant to run DDR5 strips at standard 4800MHz (5600MHz with overclocking. but our CPU does not support overclocking). At this point, clearly we need DDR5 strips specced for 4800MHz.

COOLING
These DDR5 strips run quite hot, but with no overclocking and selecting models with heat dissipators, most users report temperatures staying below 60ºC, very safely below the maximum operating temperature of 95ºC. Only a few users have reported temperatures into the 80º's: in this case a RAM fan cooler (such as the one especially made by Corsair) will low temperatures by 10-15ºC. Alternatively you may just attach an inexpensive 4cm fan over the RAM strips.

MEMORY SIZE
For my present use in photo processing and gaming, 32GB is plenty, and there are many affordable kits of 2x16GB by reputable brands. The STRIX Z690 has 4 RAM slots, allowing for future expansion.