this is a change that must happen at init time, or the sim/gui subsystem needs to be re-inited (fgcommand re-init)
It should be pretty straightforward to do this sort of thing with a handful lines of code using Nasal.
We implemented Nasal space subsystem re-initialization support roughly ~5 years ago in some branch called "init nasal earlier" in response to James asking for that at the time, because he wanted to use Nasal/PUI for rendering a launcher-like UI prior to the rest of the sim being available. Obviously, priorities have changed over time since then, nevertheless, it's still perfectly possible to detect and change fgfs defaults accordingly, in line with the GPU vendor found.
I am not very familiar with the effects subsystem, so I believe that someone like Thorsten would be in a better position to judge if any of the following makes sense or not, but as far as I remember, effects can contain heuristics in the form of so called "predicates", so that might be another way to dynamically detect/change certain default settings "on demand".