there the same compound of pad but different sizes, its just that spot pads give way better spot repairs imo
The backing plate you would need for the small pads is 70-75mm diameter backing plate, heres a link
http://www.elitecarcare.co.uk/elite-...king-plate.php
edit: poorboys compounds are very good, however i personally only use the menzerna range and some chemical guys compounds. Im sure wayne is more familiar with the poorboys range.