I kept two oscars in a 125 gallon tank that was heavily planted with potted Amazon swords. They did not bother anything, nor did I ever have to replace their heater in the 8+ years I had them. I guess mine were unique, but it is certainly POSSIBLE to keep plants and oscars together. They would uproot any 'new' plants I tried to add, and would shred anything floating. Perhaps because the decor was there before they were added, they accepted them as part of the background. Perhaps because they were HUGE established swords that almost reached the surface.
Mine would dig in the gravel, move rocks and driftwood around, and if I dared plant new plants, I would find the plant shred and pieces of it outside the tank (they'd knock the lid up while holding chunks of it, to 'show me' that I wasn't allowed to change things in 'their' tank).
Just was my experience with Felix and Oscarette (yes, a pair, but no, I did NOT name them!).