UQW is not really a 'full fledged' wax/sealant. I do suggest you use the UQW for maintenance/topping up. The 'base' need to be a proper one like ULW/UPW or DG101/DG105.
On a DA....I don't think so. Unless there's dirt inside/edge. I have one of the older Megs W8006 pad with the pad surface looking worse than that. Haven't notice any adverse effect when polishing, even with a rotary (actually, I prefer it more than the 'fresher' pads).
Would you mind elaborating about the 'coating' you mentioned. What are you looking for/preference. Did you mean to DIY or a place that do 'coating'?

http://www.wikihow.com/Take-Water-Marks-Off-Vehicles

well the easiest way is to prevent it, dry it after u washed your car, samething after exposed to rain, rinse then wipe dry

you can find megs in any ace hardware shop.

Glass or paint? Or both?

Osren has a good waterspot remover. Can't remember what's it called...I think it's stain x or something. But I've only tried it on glass...not sure whether it can be use on paint. Can get it at Osren's place in Jalan Ipoh.

Duragloss also have the #505 Water Spot Removal. Can use on both paint or glass. It's a little weaker than Osrens but it does work in removing those light waterspots/watermarks. Can buy it online or they have it in a couple of shops in PJ.
ACE Hardware

any1 going to great eastern mall for buying meguiar product?