fwiw, the main chip is the source of the heat. Keep this cool and you'll reduce the FPV issue.
Regarding the ArcticSilver thermal paste, it's somewhat electrically conductive. Any excess getting between the board and chip will have issues... The white grease originally used was silicone, not sure it was all to effective, but was less conductive. Clean either with alcohol, critical to clean from under the chip.
I prefer a thermal pad rather than a grease, as the material stays in place and performance is higher based on gap distances. The gap between the cover and the chip is fairly signification when talking thermal grease being effective. Further contact pressure is another factor to help thermal whatever be more effective.
It was mentioned back when that the chip could be re-balled and then reattached to the board. Never knew if anyone ever performed that repair...and was a success.
I have the V1 wifi module, I drilled out like the V2 (swiss cheese mod). I applied a supplemental heatsink to the wifi cover and have been problem free since the mod. Search this thread for pictures and description if interested.
3M Copper Shielding tape (RF shielding) is designed to electrical bond the two halves together, the adhesive is conductive. You may or may not have an issue if removed, depends on any gaps of the two mating parts. Aluminum tape, the adhesive is not designed for an electrical bond...ymmv