Games are starting to lose support for such features, but I was wondering if their are ways to activate both cards in such titles. Whether it be through mods, exploitation, etc.
Dual GPUs are basically already outdated now.
You are undoubtedly better just buying a newer more powerful GPU.
Not only because your doubling power draw for little gains, but most games don't support dual GPUs or are very badly optimised for it. There isn't mods that can help that, as it's how the game is entirely developed, which is not only time consuming, but also quite difficult.