Yes yes, sure. Picking the pool member (either from a persistence entry or as a result of the LB algorithm) will occur before the SNAT, so F5 will base its traffic forwarding on the actual IP it sees in the ingress packet.
And regarding the mask 255.255.255.255 this is just a mean to share persistence entries between multiple same subnet hosts, so by putting 255.255.255.255 you basically tell the F5 to create a persistence record for each unique host.
(Note: as I mentioned in my 1st answer, this assumes you don't have an upstream device -before F5- that hides the actual user IP, which is a rare but possible scenario)