Expert settings are identical to what you do on PC. It’s the plain text config file.
What might be happening is that your phone’s power management loads the Dosbox process off onto one of the power saving cores of the cpu. Happened to me in the past as well, and that caused massive slowdowns. You can try to work around that with root and certain cpu tweaking apps, but that’s certainly not a valid suggestion, as it involves tampering with your phone’s brain.
I’d suggest you try fixed cycles, and see what happens. Tie Fighter was designed for fast 386 or 486 cpus back in the day, so you should use these settings under [cpu]
What these values do:
cputype=auto: leave it as it is. There are different cpu tyoes DOSBox can emulate, but the default 80386/486 cpu is fine.
cycles: the amount of cpu operations executed. There’s no 1:1 value that relates to a certain cpu type, but these are some rough estimates:
2000 cycles = 80286 / 16 MHz
3000 cycles = 80386SX / 25 MHz
5000 cycles = 80386DX / 40 MHz
10000 cycles = 80486 / 60 MHz
20000 cycles = Pentium 90 MHz
Something like that. Cycles=max will run everything as fast as possible on your cpu, with no fixed value.