hey ive found out how to change the voltage on my gpu by using a program called sapphire trixx should i force constant voltage or not
Not.
Of course, we would need to know why you would think this is a good idea (or else, why would you be asking?). But as a rule of thumb, never force anything unless there's a reason to force it. In this case, forcing voltage sounds like a very bad idea since the manufacturer probably designed the GPU to take what it needs.
im just asking because i saw it as a option in the program so i was wondering if its needed to be turned on
also is it bad that when im stress testing the gpu core isnt staying at the setting i set it at
just watch your temps.
Again, unless there's a reason to force something, I wouldn't.
It's not bad at all if your GPU voltage levels are fluctuating -- I would expect that. But once again, if it's not working/performing as promised then that would be a reason. Otherwise, I suggest leaving them alone (unless there's some other reason to force it like if you want to test something).