[d00t]

(1) Do NOT put any wax/sealant down before getting the car clear bra'd. It will not adhere to the surface properly. Most clear bra shops should/would prep the area they were going to be clear bra'ing with a isopropyl alcohol wipe down anyways to remove whatever wax/sealant is currently on the car. So coating an area you plan to clear bra is just a waste of product (assuming you're clear bra'ing very shortly after applying the opticoat).

(2) The only problem with installing the wider footprint spoiler is, after a few years, it may be discolored from the fact that the rest of the car has been exposed to the elements over the years, and the area underneath the spoiler has not. It takes a while for this to happen, but is something to consider if you plan on keeping the car for 5+ years.