I don't think they've updated the class 3 C380+ model just yet, only the class 1 C380. I completely agree with your complaints about the screen. I would love for it to read percentage, show decimals, etc. Most other screens have sufficiently modern features. The new model with Kiox was great! In fact, that and the battery update would push me towards Gazelle.
So when riding the class 1 C380 (new model), and Avignon (also new model) bikes my wife and I really loved how quiet they were. There was a little noise, but it wasn't offensive noise. The belts were super quiet compared to chains. The shop didn't have a class 3 Gazelle model in stock, but since they have a mid step C380+ coming next week they had me try out a Reis and Muller Homage with the same Bosch motor as the C380+.
The R&M was 2X as loud as the class 1 Gazelle. I later saw some youtube videos of the C380+ where it sounded the same. Now, to be clear it was audible but not annoying. The Turbo Vado 4.0 had some nasty brake squeal, like a 15 kHz tone. I'm hoping it was because the bike had zero miles and the brakes needed bedding.
Sorry for threadjacking, hopefully it helps someone else who is also deciding between these two bikes! Totally agree that they are both very good.