The communication on this seems a bit confusing because the different phones /e/ is running on can be very different in how stuff works with them.
For the Fairphone 3/3+ it is my understanding (careful with that 
) that the install files should have the firmware bits included.
https://gitlab.e.foundation/e/os/releases/-/releases mentioned such an import once into 0.17-q, for what it’s worth.
Anyway, the two posts here and here seem to indicate that you can just install.
It might be labelled “beta”, but the Android R build you can install now is in the dev release channel already, the following builds will just be dev updates which should install OTA then, labelled “beta” or not.
If you install a dev release channel build now and later want to install a stable release channel build, this will need a new install of the OS as far as I read here. Whether you can keep your data when doing that … I can’t seem to find a reference.