The update is the same for all four devices. It is marked differently, but the changelog is identical. This update is coming to the OnePlus 7 and 7 Pro as Open Beta 13. In the case of the OnePlus 7T and 7T Pro, it's called Open Beta 3.
The camera dirt detection is the most notable change in this OnePlus 7 & 7T series update
Now, once you install this update, you'll get a new security patch as well. The update brings the Android security patch for April 2020. The camera dirt detection feature will let you know when you need to clean your camera lens on the OnePlus 7 and 7T series.
The company has also optimized the volume adjustment in this update. A missing recording icon in the call screen has also been added. Various other issues have been fixed, and system stability has been improved.
This update also adds the ringing duration information for missed calls. You can also switch your mobile data on phone calls supported with VoLTE now.
That is basically everything that the company mentioned in its changelog. This update doesn't really bring a ton of changes, but several issues have been fixed, while one feature has been added.
You can expect the camera dirt detection feature to be pushed to a stable version in the near future. This update is rolling out as we speak, but you need to be on a beta channel in order to get it.
The update is now rolling out OTA for those of you who run beta software already
The update is rolling out OTA (Over The Air), by the way. If you're not running beta software already, you'll need to install it manually. You will not lose your data when you install it, but you will when you revert the process.
There is no way for you to install a stable build when moving from a beta channel without losing your data, unfortunately. So, if you're not ready for that to happen when you move back, don't install beta at all.
It's also worth noting that some issues are possible, as this is a beta build after all. OnePlus' beta builds are known to be quite stable, but still, issues are a possibility.
If you know what you're doing, and are ready to make that step, go for it. You can find download links for the Open Beta 3 and 13 via this link.
Installing a beta build if you're running a stable build is really easy. All you have to do is download the right file, and install it via your phone's Settings. You can find more information on the provided link in the previous paragraph.