So is the key to avoid "gap" issues over time with the spoiler fitment just ensuring you do not overtighten the mounting screws?

Is there any point in waiting to do the spoiler at the same time as a backup camera install (like to use the same drilled holes, etc) or are they totally independent in terms of work required to do both?

 

No common holes, but you do have to remove the inside trunk lid cover and the inside trunk covers to get to the wiring. You can find the instructions to both in the garage thread

https://acurazine.com/forums/2g-rl-2005-2012-76/2g-rl-garage-version-1-1-acura-servicenews-diys-tsbs-etc-738410/

If you search, there is also a DIY on the spoiler, including one where no drilling was done, and they relied on heavy duty double stick tape.

There is also a camera DIY of sorts, actually it is installing an 07 base model camera, which is very close to the installation of an 06 camera.