Welcome Legendary Rob. I've recently picked up a PC Engine Duo myself, i had the TG16 back in the day but it was sold around college years. Started getting back interested in the console again (Happy Console Gamer and BitHead1000 videos didn't hurt).
I may be preaching to the choir, but if you have not played Ys 1 & 2 yet, i'd make that a target - you'll need a way to play CD's of course.
One still cheap HuCard out there is Final Lap Twin - the only reason i recommend it is due to the RPG - I haven't played it in decades but back in the day i had a lot of fun with it....or maybe i was just excited an otherwise mediocre racing game turned out to actually provide some decent hours of gaming...would have to revisit but again fond memories.