There is no option in settings to control volume, be it sfx or music or master. Also, there seem no higher-grade cutscenes to momentarily escape the rpgm layout for any impactful moments.
In the System menu, there are BGM, BGS, and SFX controls.
Yes, the game is made in RPGM. If you mean that to be feedback, you'll have to be more specific.
I wss blind as a bat about sound. Still, the the demonic showpiece has render problems. Also, flash/etc cutscenes are possible, regardless of RPGM.
You're playing on mobile? You can if you want, but it isn't officially supported.
Not everybody has a choice. Either fix it or don’t.