Baseboard heat - Installed and then drywall around
I do not think that you will be able to use any of the products you mentioned since they both fit over the whole wall mounted baseboard enclosure. Your enclosure is installed as you said, with the drywall set on top of the enclosure so you do not have access to the back of the enclosure. I have only seen this type of installation done once before. I do not know the company that installed them that way but "what a mistake". You will probably be limited to either painting what you have or trying to buy new enclosures from the same manufacturer as those installed. Good luck in your search for a fix.