Recommended parameters
ASTC
Usually I use ASTC_4x4 or ASTC_8x8 compression with quality astcmedium.
ETC
Usually I use ETC2_RGB or ETC2_RGBA (with alpha channel) compression with quality etcfast.
PVRTC
Usually I use PVRTC1_4_RGB or PVRTC1_4 (with alpha channel) compression with quality pvrtcnormal.
S3TC
Usually I use DXT1, DXT1A (with alpha channel) or DXT5 compression with quality normal.