I own the top loader Japanese NGCD.
None of the Neo Geo CD Systems have regional lockout. You can play US or Japanese games on either a US or a Japanese system. If you purchase a Japanese game CD and you have a Japanese system, it will depend on if the options menu gives you the choice of languages or not. Some games are "Japanese only" and they are few in number. Below is a list of those games,
ADK WORLD [ADK SPECIAL]
KING OF FIGHTERS 96 NG COLLECTION
MAHJONG FINAL ROMANCE 2
MAHJONG KYO RETSUDEN
MASTER OF SYOUGI
NEO GEO CD SPECIAL
QUEST OF THE JONG MASTER [MAHJONG JANSHIN DENSETSU]
QUIZ KING OF FIGHTERS
SAMURAI SPIRITS RPG
STAKES WINNER
I understand from those who have an English system that all games besides the ones on this list will play in English on an English region system. The English system also edits out the blood and the bouncy, bouncy.
I have only one game that is a Japanese CD that does not give me the language option and that is Samurai Spirits 1. I own 24 games at this time.