Sticking with mostly the US library may make sense with most systems, but it really, REALLY doesn't with the TG16; even the Saturn has a better US library than the TG16 does, and US Saturn games are on average much cheaper too. Sure there are some expensive Saturn games, but there are a bunch of cheap ones. TG16? Not so much, almost everything except for the most common stuff (sports games, Keith Courage...) is pricey.
And as for the US CD library... yeah, almost all of them will cost you.
Now, there certainly are games which will be better in the US versions, thanks to language issues. Games with lots of text or voice acting, such as many of the CD titles (the ones with voice in them; some, like Terraforming, Buster Bros/Pomping World, and the like, don't have any) or HuCards like Dungeon Explorer, Neutopia, Dragon's Curse, and the like... I'd get US versions of those games, yeah. But with so many other games you'll spend a lot less for the exact same game if you get the import; the only difference really would be a Japanese-language manual.
Oh yeah, and in late '92 to mid '93, TTI stopped using jewelcases for US HuCard releases. Go look it up -- those games just have a plastic tray inside the outer cardboard box. This means that you'll either need to spend the significant sum to get it complete, or just deal with card-only for those titles. '89 to '91 (and maybe early '92) US releases do have jewelcases, so for those I don't mind not having the outer cardboard boxes, but the later ones... I don't own any of those games' US versions yet, both because of the cost and the packaging issue. All CD games do have jewelcases though, at least.
I know that language is an issue, and getting many import games for this system WILL end up with you having games with lots of Japanese in them, but there's really no way around it if you want to see most of the library. And anyway, the shmups don't require language, and many of those are import-only. Some are expensive, but not all.
As for places to look for reviews and the like, two of the best, I think, are
The Brothers Duomazov and
Video Game Den. Both have extensive review libraries on their sites. There are some other good sites too, though very few have as many reviews as those.
Also I've started to do some myself, of course; so far I've done some
TG/PCE CD game summaries (regular CD titles only so far), and full reviews of
Avenger and
Hihou Densetsu: Chris no Bouken.