I have a 7K boat and I too have tabs. Mine are no where near the rudder though. My rudder is down much deeper, under the hull more, the tabs are not wide enough, and there is only one rudder, not the two as on the boat above.
1---They do help reduce turbulence when travelling. I cannot really detect any speed change but I can hear a change in the engine note so they do have an effect.
2---Another effect I noticed is between up and down the stern wave is noticeably reduced when the tabs are down, especially when the boat is heavily loaded at the start of a cruise. Enough so that when travelling and I look over the dinghy top I can see the wave when retracted. When the tabs are deployed then I cannot see the wave over top of the dinghy.
3---They can change a list once the boat is moving.
If the boat is a full displacement or close I would expect they would be of little use, maybe just a nuisance.
However, my boat and the one shown above are S.D. or more of a planing boat so trim tabs can have an effect. Good or bad, it is how they are used or misused.
In rough following seas I definitely retract them or they can help to force the bow to dig into the wave ahead maybe causing a broach, at least harder steering.
It does look like that one tab contacts the rudder top from the paint rubbed off. Maybe trimming the rudder a bit would get more down movement from the tab which , if the rudder contact is fact, could be worthwhile. If the tabs cannot go full down from rudder contact then they cannot do the job they were intended to do. It's not that they cannot help, they are prevented from helping.
If the rudder is trimmed to allow the tabs to work properly then the three effects I outlined above may come into play which will help the boat, mildly yes, but still help. Since the tabs are already installed, consider getting them to work properly.
BUT in rough following seas be sure they are retracted.