Nice pickup on the TG-16. I have one myself with an Everdrive (I decided right away I could not commit the $$$ required to play the best games). One question - how do you connect it with the HD Retrovision Genesis cable? I have two such cables. Right now I use an aftermarket TG-16 composite adapter to connect it to a CRT. I don't have a TG-CD or the CD adapter you have.
So I had been using a TG 16 with an everdrive for a while. The device that I just got basically has a built in everdrive and it has the genesis 2 port directly on the unit. Here is how it connects...


However, from what I understand, ALL TG-16s have the ability for RGB out. It's just a matter of modding the console or using the right accessory. For a few years I have been using this...


It isn't pretty, and without a shell it's fairly fragile, but it taps in to the RGB signal. I never used the actual component ports on it, instead using the genesis 2 port with the retrovision HD cables. I got this on eBay for about $20 a few years ago. The seller is still making them:
https://www.ebay.com/itm/PC-Engine-AV-Booster-RGBS-output-TurboGrafx-16-Composite-RCA-RGB-SCART-/153434964442?oid=152607382167Yes, I'm sure these are cheap, and better (more costly) solutions are available. But this thing has made my TG16 look great for the last 2 years.