Oxygen is a plant waste product, so it makes sense that plants won't thrive in an environment high in O2.
This is absolutely untrue
co2 is a fish waste product but with good oxygen levels they survive in much higher co2 levels. plants likewise share a symbiosis with bacteria which only benefit frm higher oxygen levels.
a little theory on bacteria is that efficient bacteria can promote nutrient uptake by the plant, but that is theory
there are many of us out there with wet/ dry filters with higher than normal oxygen levels
Tom Barr has tested and during the light cycle is getting around 125% saturation with oxygen levels, and his plants grow great, my setup fairly mimics his i nthat im high co2 and light, with a wet/dry so im not far frm that number if not higher, and my plants grow great when im injecting the ever illusive co2 properly.
some have even tested injecting oxygen into planted tanks with pure oxygen to see if it was detrimental to algae.. it was not, but at high enough levels it oxidizes fish flesh and can be very lethal
for our ranges though, it does not affect a plant to have high oxygen levels, bubblers do destroy available co2 levels and THAT will definitely negatively impact plant growth
TO the OP
oxygen is increased by gas exchange at surface water. the more surface area you have for a volume of water, the more oxygen will be bound to water.
this can be done by having a thin sheet of water or by increasing surface agitation whic creates waves and thus mroe surface area. Circulation also plays a huge role here as if the only water that's being moved around is that below the surface then not much gas exchange is occuring. this is wh its important to have good flow throughout the tank to distribute oxygen properly AS well as having good flow at the surface to distribute oxygenated water..
HOB's are pretty good at it actually. just don't let the water fall too much, that doens't circulate well, its stead have the water about the bottom of the return and this will force water around the tank and increase surface movement.
Also oxygen levels are decreased by bacteria that is processing organic material in the tank. remove organics needing to be processed " food, poop, decaying plant matter, etc" and you will increase available oxygen for fish.
best way to do this is good filter maintenance habits, good water changes, and a clean substrate