The P is the number of poles - how many actual switches are inside the switch either a number of S for single, D for dual, and T is toggle - how many ways each individual switch can be switched. Eg DP4T has two separate switch, each common can connect to 4 nodes.
If you just need to pull a pin low/high then you only need one toggle, and one pole - SPST. But you can of course use SPDT as you just need the NC (normally closed) unconnected. And you can use DPDT and just leave one whole switch unconnected.
In my experience, you narrow down the search first by type (slide, toggle, rocker etc..) then by termination (PCB, solder lug, tab, screw terminal).