Keep in mind that emulation is different than running code natively. It’s like speaking a completely foreign language using only a dictionary, without any prior knowledge of that language.
A 2018 phone is more powerful than a 2008 PC, but it doesn’t have an x86 cpu, and doesn’t run DOS, so it can’t run DOS games natively.
At any rate, your S8+ has enough horsepower to run even demanding DOS games or even Win95. At least if it has an Exynos cpu, I’m not sure if the Snapdragons had already caught up back then (they have today, and are even faster, I think).
Judging by the scores in the benchmark section, you should be able to get a score of ~700 realtics in the linked Doom benchmark.
In this particular benchmark, I had the aforementioned performance drops due to unnecessary performance throttling. Sometimes 610 realtics, sometimes 900. Game Tuner & root fixed this for me, but the issue remains. And it seems to be a Samsung issue with the S8 and S9 series. S10 is fine again. ¯\_(ツ)_/¯
What you can do for testing: download the shareware 1.9 version of Doom, set it up in Dosbox, and run it with different cycles settings (cycles= max 105%, cycles=50000, cycles=100000, cycles=125000, etc.). At some point, you will get sound crackling issues, that’s when you’ve reached your cpu limit.
Run the demo with the following command:
doom -timedemo demo3
and see what happens.
Again, you cpu should be powerful enough to run even Win95 games like Diablo or Commandos.