I would use one. They do clog quickly. I actually don't use the manufacturer's polishing pads in any of my filters; I use generic filter foam, sold by the metre, and cut it to fit. It's just as good and an awful lot less expensive:
Full flow is best unless any fish struggle with it (some species don't like flow). As yours seem happy with it, leave it as it is. As far as the bubbles go, just have it set to what gives a pleasing effect as, as long as there's disturbance at the water surface (just rippling really), there will be plenty of oxygen dissolved in the water.
The last tank I set up had a reverse flow undergravel filter - which was seen as sophisticated then! Now, I've got a 40 gallon (36x18x18) with an intank corner filter using a "cotton" mat and bio balls.
Question about the bio balls - I know not to clean them - unless something goes drastically wrong - but, during a water change, should I stir them so the wet become dry and vice versa, or leave them as they are?
Fishlady wrote: Leave them be - disturbing them (particularly letting wet ones dry out) will upset your beneficial bacteria.
Thanks, I did ask in the shop, but I'm living in Thailand now, didn't have my organic translator with me (wife) and the shopkeeper, who appears very knowledgeable, has almost no English. So it was sign language and "point 'n grunt".