GPU rendering won’t help. Samsung’s cpu management is a mess, so it’s not unlikely they re-configured cpu throttling, to prevent heating and increase battery life, who knows? What phone do you have btw?
You can use Game Launcher or better (if still available) Game Tuner/Game Tools, to activate a higher performance profile for Magic Dosbox. There should also be a high performance option somewhere in the quick access tiles of your phone.
The cycles=120% setting will increase emulation speed, but at the expense of sound quality. Anything above 105% can lead to sound stuttering/crackling, because you’ll be running Dosbox above your cpu’s speed limits.
Frame skip, at least on modern phones, has close to zero effect on performance. I’d rather set it to 0 or 1, so you’ll get a smoother gaming experiece. There’s no point in increasing emulation speed, when on the other hand, you set video output to 10 or 15 fps.