AirAlo seems to be the best service. If you get a good discount, it is great. If you're traveling, it is the one you can trust. If it was more affordable, it would be my only option.

I purchased an 20GB eSIM from Airalo for my trip to South Africa. Installation process is very easy using their app.
I used a lot Google Maps, Waze and Uber, as well as Facetime and WhatsApp to send lots of videos and pictures. And it's cool that you can track the amount of data left in the app. 
Overall, I would definitely recommend Airalo eSIMs.
Only 4 stars because no 5G only 4G ;)

I used Airalo and Nomad in Hokkaido when I was visiting Japan. Here is my review for Airalo.
I had a great experience overall: setup of the eSIM was very smooth, but I was a bit disappointed with bandwidth speeds eventhough it was acceptable. 

I purchased Airalo's Moshi Moshi 1GB plan which is only compatible in Japan and is a data-only plan.

The good : 
- Airalo's user experience is very good. The eSIM setup was very simple and was mostly about clicking on buttons through the entire process.
- I was able to roam on the NTT Docomo network in 4G, which is really efficient in Japan. I did a few tests and was about to get roughly 80.6MBS download and 8.6MBS upload speeds. So great download speeds. Upload speeds could have been better. Airalo also advertised the eSIM as compatible with KDDI (another network provider) but I did not try it. 

The bad :
- Too bad I did not get 5G it was a bit frustrating because my phone is 5G compatible.
- Since Airalo is not a local network, my internet traffic was routed through Singapore, which is a bit far from Japan - so latency was not the best

Airalo: Geschwindigkeiten und Netzwerktests

Airalo

Airalo : durchschnittliche Leistung

Airalo : letzte Geschwindigkeitstests und Netzwerktests