[Quoth]

Sony DPT-S1/DPT-RT1 are same HW as some Fujitsu models. I looked at the Sony DPT range and it is awful to communicate with and other HW shortcomings.
A reMarkable is a 10.3" copy of the same idea and I gave mine away, my Elipsa was far better.
But I got a Sage after the Elipsa and much easier to hold (8") and more pixels because a 300 dpi vs 227 dpi screen. I also stopped using the Elipsa not long after getting the Sage and then gave it away too. I don't miss either of my 10.3" eink models. I think pointless.

The Amazon Scribe is 10"+ and 300 dpi, but Amazon expect you to use their server, not direct PDFs, though it can sideload them. I considered it, but the more users here wrote, the less I wanted it.

TCL is confusing and so are their Nxtpaper models. There is a far more expensive Pro version of the Nxtpaper 3.0 based Nxtpaper 14. The main difference is gaming support / faster refresh. There is zero advantage to it for PDFs or Web browsing. That 14.25" on 3:2 aspect makes a huge difference compared to 10"+ or the largest 13"+ size Sony/Fujitsu eink. The earlier S/H Sony DPT & Fujitsu are quite low resolution. Most or all have no front light. Some 10"+ eink have no front light.
I almost never use the front light on my eink, but if I'm out somewhere then that place might need the front light.

Avoid TCL Nxtpaper 1.0 devices if you want outdoors. They are about 1/2 brightness or less.
The model numbers also don't always relate to inches and aspect ratios vary dramatically. The Nxtpaper 11 is approximately 16:10 (Nxtpaper 2.0) and good for notes. A pro version will simply be more CPU or refresh or pen included or something at the same poor 16:10 (for PDFs). The Nxtpaper 14 is HUGELY better for PDFs (3:2 14.25" vs 16:10 10.9") than the Nxtpaper 11. Certainly the Nxtpaper 14 pro is expensive and really only adds faster refresh and aimed at gamers!
Also some models are OLED and some LCD.

On NxtPaper 40 (Nxtpaper 2.0) and NxtPaper 50, the 4 & 5 indicate 4G and 5G, otherwise similar. Reviews suggest the NxtPaper 50 is not as good a phone, but that could be flaky 5G service, which is only of value on a racetrack, sports ground or an auditorium; 5G is rubbish for urban or rural coverage due to wavebands used. my Nxtpaper 40 is fine.