While going for another program, ideally non proprietary, with a native Linux version would be ideal, I would not be surprised if running Photoshop on Linux with wine was a viable option these days. Or will be in a not-too-distant future.
As for games, what the others have said. Unless you're into a specific multiplier game with a kernel level "anticheat", then it should be fine.
In fact, I suspect Photoshop, rather than gaming, is much more likely to be the reason you'd have to dual boot.