Onyx Boox Max 3

Now my personal recommendations for different screen sizes will be Onyx Boox Max Lumi for 13.3'. It's the best in that size. For 10.3' size, my suggestion will be to go for Boox Note 3. Even though Note air is also a great option in that size, I won't recommend it for your use case because you said you will use it on the go a lot.

If you can find Onyx boox poke 3 around 150-180€, it can also be a decent option. Very fast android device at 6". Excellent native app (my favourite), you can download your dictionary so you can buy oxford and donwload it to the device, very agile due to android (9 or 10 version) and finally extremely small form factor. More like a 5" device chassis with a 6" screen.

I already found the onyx boox poke 3 that seems to match all my requirements but after watching some video reviews I'm very disappointed about the screen responsiveness. On paper the device has very good specs but Android isn't optimized for eink devices and the screen is very laggy for this usage. I watched a YouTube video where the turn page speed is a bit slower than Kindle Paperwhite 2021. I was also considering on getting a Kindle Paperwhite 2021 and use the integrated web browser but it doesn't seem offering a pleasent user experience.

The Max 2 was somewhat slow for my needs and also the screen broke easily because it is unprotected. The Max 3 has a proper flush screen and is more durable.

My front runner for an ereader is Onyx Boox Poke 3. It's an android based ereader so you can download the usual reading apps* to the reader and not be locked in to a store. I've heard the Kobo's warm light is very easy on the eyes. I really like the Kindle dictionary and search functions on its app (all apps have dictionary/search but the Kindle do it very well).