It's very easy to get to Disneyland from central Paris via the A line, as it's the last stop. The journey takes about 45 minutes. This year, the fare has been reduced to 2.5 euros, making it quite affordable. From the station to the entrance gate, it's a short walk, less than 2 minutes after the security check. Admission was seamless; I simply showed the QR code screenshot on my phone to be scanned.
Last year, I visited Hong Kong Disneyland, and I'd say the crowds here were slightly larger. I went on Tuesday, September 2nd, a weekday just after the summer vacation, expecting it to be less crowded, but it wasn't as empty as I'd hoped. However, the longest I waited for a ride was 40 minutes for Big Thunder Mountain, which is nothing compared to Tokyo.
Many reviews say restaurant reservations are essential, but there are plenty of takeout and self-service options available, so you'll be fine. A burger set cost around 4000 yen, about the same as food prices in Hong Kong.
Europeans seem to love Mickey Mouse as much as anyone else; I saw many adults wearing headbands that cost 25 euros (about 5000 yen).
The return trip was also easy, as it's the first station on the line, so I was able to get a seat and relax all the way back to the city. I didn't feel unsafe at all. Also, on the way there, I noticed some young Japanese women who I assumed were headed to the outlet mall located at the station before the final stop.