How well does T-Mobile work in Japan? (Tokyo/Osaka/Kyoto)

Hi!
I am traveling to Japan (Tokyo/Osaka/Kyoto) and have T-Mobile Magenta plan with the unlimited roaming to any destination/unlimited data etc. It says it works fine in Japan on when I check the website. HOWEVER . . . I have checked my previous two trip countries, and to be honest, the data and network was very poor - even though on the website it says it works there.

I recently went to Sweden - Stockholm (in July), and Jamaica - Negril (2 weeks ago).

I couldn't access maps, or the internet very well. Some places it was OK, but mostly had to use WiFi.

I don't want this issue in japan, so I am just asking if anyone has had better experience there with T-Mobile than I have had in the previous two countries I visited.

Thanks!