Here is my bytes to the questions
2: This enable the ActionReplayMK3 ROM feature of the core.
If an AR3.ROM file is present at the sd-card root, it will be loaded into S-RAM at boot-up (and/or PGM_RESET). After that, the AR3 module is active and accessable via R-CTRL+BREAK keys.
If there is no AR3.ROM file in the sd-card root folder, the whole AR3 option is inactive, even if set "enable" in the OSD. No S-RAM will be used.
3: The Turbo mode affect is not limited to the CPU clock speed.
The Blitter also is speed-up, there is no more "blitter slow down".
At the same time the Floppy transfer speed can be faster (free DMA channel can be used).
This speed-up may be incompatible to some title.
4: Audio volume generation is the same as in real Amiga hardware and only external adjustable.
It could be possible to provide an OSD volume control, but better to use external adjustment.
5: This is quite impossible to solve.
It would require an "intelligent hardware detection" to guess current chipset function (bitplane, sprite, copper...).
But the AR3 provide a more or less good screenshot feature, try the "p" and "sp" command.
6: In my core the BLK scanline option optical is the same as OFF = no scanlines effect visible. Additionally the CPU cache at Turbo mode is disabled.
This may help some title having problems with a really fast CPU + cache. The clockrate stay the same (42/49 MHz) but the cache will boost the programs running in the SlowRAM and the whole Kickstart area.
If a program/game... run too fast, try the BLK option. Else just select OFF or DIM for full speed.
7: This feature is not available.
Minimig core has no direct sd-card access and also should not have
The risc of a filesystem trash would make the whole card unuseable and Minimig would not operate any more until a matching OS (like Windows) did a repair or reformat.