Yes Betacam is backward compatible with Betacam SP both formats are analog and the deck should playback both form factors the big and small cassettes. One thing about connectivity, if you are digitizing and seeking perfection you would want to capture from component not S-Video, component is the nature of the format, the deck may conveniently convert to S-Video but a slight quality is lost.
Ultimately you would want a SDI out and SDI PCI acquisition card or USB device to transfer the digital stream to computer, I can recommend 2 Sony decks J-3SDI and J-30SDI, both units are identical except the J-30 has an extra DV port which no one needs, Both decks are just players but can playback all 5 SD formats digital and analog small and large cassettes.