Seems like different people get different results and have different preferences when it comes to wax on/off by hand/machine. I do it all by machine except for applying Souveran, KSG, and UPP, which just go on better and thinner by hand.
HEMMISSEY- Think of it this way- the polish does some minor abrading of the paint (very minor in the case of the stuff you have

), so you want to use it on *bare* paint. If you put the wax on first the polish would have to cut through the wax before it even started to do its job. The wax is a final-step product (around here we call it a Last Step Product, or "LSP") that seals in the polish and protects the paint with a sacrificial barrier; the wax takes the abuse from the elements/etc. so the paint doesn't have to.
Sealants are, IMO, best reserved for vehicles where you can basically get, and keep, a perfect finish. Waxes hide little flaws better than sealants, and give a different look too. I'd stick with waxes for now while you learn your way around this whole detailing thing.
There shouldn't be any problem using the buffer *BUT* you gotta be careful about the bonnets/pads that you use. Many of the cheaper buffers (the 8"/10" types of buffers liket the WaxMaster) come with pads/bonnets that aren't soft enough and will mar your paint. Working by hand is very safe (as long as you use nice soft stuff to apply/remove the products) but buffers are safe with the right pads/bonnets too. People who say that, categorically speaking, buffers are bad simply don't know what they're talking about. I've been using them to polish and wax since forever...it works fine.
Oh, and welcome to Autopia!