It is also my understanding that US and Euro systems are the same as far as the hucards are concerned. So I'd also say in answer to your two questions... Yes on both.
Also, as others have said...
Keep your US TG16 for all the US (or Euro) hucards you want to play.
Then ideally, find a PC engine Duo R or RX system. That will cover 98% of all the games US or JPN, hucard or CD. -- Expect to spend $150 to $200 for a good one of these systems. Well worth it!
If you want to play the handful of "Arcade Card" games, then you'll just need an Arcade Card Duo CD system card -- Expect to spend about $30 to $40
If you want to play the 5 (7) SuperGrafx games, then you'll need to get a Supergrafx console. -- Can be found for $100-$150 or so...
If you want to play the dozen or so LDROM2 games (Laseractive Laserdisc games) then of course you'll need to spend a bundle on a Laseractive and either a US or JPN PAC. Expect to pay $200 for the base unit and another $250 for an NEC PAC.
If I havent confused you, then I apologize, I'll try harder next time
but give this guide a read, it explains WTF is going on with all these different systems / cd systems etc.
http://pcenginefx.com/main/nec_compatibility_guide.html