Not as good as ONR but for that price is quite good already. Got it from Tesco.

Yes, you can go with speed 4 or even 5. Personally, I'd go for higher speed for compounding (and to answer your second question) to compensate for the light pressure so that the pad will keep spinning (not bogging down). The newer compounds and polishes (like UC & UP) will still work even with light pressure, albeit slower and requires more passes. And, like you mentioned, exerting more pressure would slow down the spinning (and even bog it down - not spinning at all), hence reducing the ability to correct. So, you're better off using light pressure with higher speed....more efficient that way. For the polishes (like UP), work using 'zenith' method - 1 pass at slower speed (2) to spread the product, a couple of passes at higher speed (4~5) to work then finally another pass with slow speed again (2~3) with *almost* no pressure (only weight of the machine) to 'refine' the finish. Just to give you a rough idea of the speed of your arm movement, a typical single 'pass' (eg. going one round horizontal then another round vertically) for 2' x 2' area would take around 2~3 minutes or so with the UP. Plenty of video online on how 'fast' your movement should be when using a DA and the same could apply when using an ROB like the Bosch.

Also, do take note that having the face of the pad not evenly flat on the panel (eg. tilting a little) would also slow down/stop the pad from rotating (and sometime it would even spin in the other direction), so you'd have to play around with the angle you're holding the machine to maintain the spinning.

Just a suggestion, for defects at isolated areas (small areas) or spot corrections (eg. scratches, bird poo, etc.) you could first try removing the defect using the UC by hand with a cloth or applicator, then only go over the area again with the Bosch. Using the UC by hand and with point load pressure (palm or finger/fingers) would be more aggressive and remove the defect quicker, furthermore you'd only be 'cutting' the AFFECTED AREA and avoid unnecessary 'cutting' of unaffected areas.

Well, for starters, I'm no Sifu, just another guy who does his own cars and some.

Conventional wax are not permanent coatings, permanent coatings are stuff like the OptiCoat, OptiGuard, Cquartz, anything that, forms a permanent bond onto the surface, and crystallizes(from liquid turns to glass/solid) if you leave it in open air.

Well, it's always recommended to clay as a form of old wax removal and also to remove any contaminants before a new coat of wax/sealant. Also, well, we won't want to seal the contaminants along onto our paint work when we apply the new layer of wax/sealant, right? But, if your car was recently clayed and waxed/sealed(maybe say about 2-3 months? Actually it's hard to judge other than to feel the surface after a wash), then, a cleaner wax is good enough to remove old layer and apply a new layer.