That pump is max 1500 PSI. You could run an 08 tip at 1800 PSI with a 5CP2120W at its max RPM. The 5CP6120 is max 7.4 GPM, so you could run a larger tip than 08 at 1500.
Length of wand just needs to fit your and your customers' needs. I've seen a wash with 6' wands, kind of ridiculous since his bays aren't even 14' wide.