That’s weird, the S7 shouldn’t have any problems whatsoever. My S9+ can run the game fluently at 800×600, and the S7 Exynos isn’t much slower.
Here’s a short video I just recorded on my phone: https://youtu.be/Y-tARzkeNyA
Mind that there are some minor stutters in the video that were caused by the recording, the game runs even smoother.
You should configure Magic Dosbox in Game Launcher, or even better, Game Tuner (if that’s still available for your phone) to run in performance mode.
These are my settings:
#valid cputypes (Ykhwong SVN):