COPRO PGA/PLCC is space for a Motorola 68881 or 68882 Floating Point Unit (FPU) that speed up math calculations and is requiered for some software to work but doesn't speed up the computer in any other way. They exist in PGA and PLCC design and you should only use on or the other, not both. By default an installed FPU will run at 14 or 28Mhz since it get it's clock from the Amiga but there's space for a oscillator and jumper to run asyncron if your FPU is of a different speed.
If you don't have software that requier an FPU or work alot with archives it's hardly worth it.
The card need simms that run in at least 70ns. That meens anything 70ns or lower (faster) should work fine where 80ns and higher (slower) wont work. Simms usually specify this and if they don't check the chips as they are usually marked with their speed such as -7 or -70 for 70ns.
