I don't have any good "rule of thumb" about spools being more/less effective with particular bottom pins (other than the general observation that "balanced" pin stacks have some good security advantages).
In terms of mixing standard and spooled drivers, though, that's an absolute requirement. If you pinned a standard lock entirely with standard spool pins, it would be a real pain to use. Without at least one standard driver pin, the cylinder would be free to rotate slightly in either direction all the time; unless you were very careful when starting to insert the key (to keep it perfectly vertical), even the slightest twist of the cylinder would immediately bind the drivers and prevent you from inserting/removing the key. (This was an early lesson when I first got a handful of spooled drivers to play with... it took me a minute to sort out why the key no longer fit into my practice lock.)
