In general yes, but often it is a problem to set up vectoring dsl.... Let your current OpenWrt install cool down a bit.
I'm a little confused. We seem to be talking at cross purposes. I don't want to display any Fritz! functions on my Fritz!Repeater 450E, which is currently running OpenWRT. My Fritz!Box, on the other hand, will remain as it is: with Fritz!OS as my router (and without OpenWRT).
I was just thinking about what I could try next on the Fritz!Repeater... as soon as I have the time. A guest Wi-Fi network, which shouldn't have access to my main home network, was one idea. Are you referring me to that?
You can make a guest wifi behind double nat in addition to default bridge wifi.