Gnome and KDE (The current version is also called Plasma.) are generally touted as being the most touchscreen friendly desktop environments, so go for a distro that has one of them as an official flavor. You’ll wanna keep your physical keyboard around through the install process until you get the onscreen keyboard set up the way you want. (The touchscreen is not going to work during the UEFI/bootloader stage, so the physical keyboard is not just a suggestion but a requirement.)

Right-click through touchscreen being set up out-of-the-box, I have only seen in Gnome. Gnome also has the onscreen keyboard pre-installed. The whole Gnome layout works well with touchscreens. It is a bit different from Windows, though.

One downside to Gnome is that for some reason, the screen scaling is limited to 100% or 200%. This can be annoying, since 1x scaling frequently makes the buttons too small for a touchscreen, but 2x is way too huge. You can install “gnome tweaks” to get 150%, if it even works properly on your distro. If you want 120% or some other number, then you’re outta luck. Increasing the text size can help, but then the app labels in the app drawer get cut off. This all seems like a huge oversight to me, personally. Even Windows allows custom scaling percentages.

I have a touchscreen device myself (1st Gen Surface Go), and I’ve found Gnome to be the best suited to touchscreens. However, I personally can’t stand it. I previously tried KDE but left due to lack of right-click support. I’m planning on going back and just living without it.