Japanese version is probably very close to the tactical game, with a lot of random of course. Over the course of several full games in a row, strong players are consistently ahead in the ratings even if they are set back by some random big loss in a single game. It is not a chess or go level of course, but also not a simple solitaire with tiles game anymore. The main tactical problem in the riichi is that discarding someone's winning tile makes you responsible for full amount of points, and to avoid that you need to discern what could be such tile just by looking only at the discards and player actions, which is possible for high level players.
