Unless you do tent mode, 2n1s really are not feasible for your use, and that leaves basically just the Galaxy Tab Ultra.
Oh wow, I somehow missed the S10 launched. Also, ugh at that price and it doesn't seem to offer much over the S9. I thought maybe they were using a tandem OLED, seeing the 2X marketing, but the S9 had 2X labeling as well. They offered pretty good trade-in deals on the Tab line, so might check out what they're offering for trade-in.
Looks like they add some form of anti-glare, which might be a good thing or bad thing depending on your opinion (negative in mine, although it probably would help if you use it outdoors much, but I'd much prefer if they made that an option in a case; Samsung makes cases that do similar, either to add "paper like" feel for stylus or for privacy).
Also the switch to Mediatek SoC could be good or bad depending on your opinion. Their site says both the Ultra and + offer 5G, but can only buy Wifi versions? Maybe that's only outside the US since they ditched Qualcomm.
Shame Samsung won't make the device that Apple refuses to, which would be something like the old Surface Book, only with a viable tablet portion. Samsung could offer it a couple of ways too, by building DeX into a fullblown Linux distro (FYI, if people didn't know, Google is kinda doing this themselves with Android, there's a new desktop mode that can be enabled in Developer settings on Pixel 8 and 9) that can be used on device when the keyboard is connected, or when plugged into an external display. Or they could do a "Pro" model that uses Windows and the Snapdragon Elite.
I went S7+ -> S8 Ultra and initially tried downsizing to the base S9 as it offered everything the largers sizes did that gen, but it was too small so I went back to the Ultra (already had a case for the S8 that I liked, it required trimming a bit of the case around the camera area but fits), thinking I might use it as a sorta laptop replacement. Also had a pool at the time so the waterproofing of the S9 series was appealing. But I ultimately ended up not really using it for a variety of reasons (size, stylus of the Samsung tablets is not good quality). Its a good tablet (and one of the few Android devices that still offers proper multi-user where you can switch from the lock screen). I definitely prefer the 16:10 ratio of the Samsung tablets over the 4:3 of iPads.
Another option possibly worth considering is getting an portable monitor and a USB-C cable. I got a Viewsonic 15.4" 4K OLED on eBay (refurbished direct from Viewsonic, it sure seemed brand new in box though) for $250 and it is very nice (very thin other than the small I/O section but its built in as an integrated stand), and USB-C allows both power and display, and can use it out of your phone even. You'd either have to figure out some other control mechanism (mouse? Or if you just need simple page turn capability could get a remote of some sort). There are some portable monitors that have touchscreens too. For the size its lighter than tablet/laptop, and with a low profile (but proper quality) USB-C cable you can use it on a variety of devices. Its also light enough that could probably clamp the I/O section down with one of those articulating bendable arms.