Usually single sided 40-track 3" disk drives are used in CPCs. For practical purposes, 42 tracks could be used — the limit is specific to the drive and some support more tracks but 42 is a good maximum.
The FDC controller can be used to control 80-tracks and/or double sided drives, though AMSDOS doesn't support such formats. To use 80-track drives and/or dual-head drives, you need to use another CPC DOS instead of AMSDOS. The most popular one is [[ParaDOS]]. It can handle up to 796 KB instead of 178 KB for AMSDOS.
Half of the original AMSDOS rom is occupied by [[Dr. Logo]] from Digital Research. If you replace AMSDOS with ParaDOS, you will lose access to Dr. Logo.
Even with an AMSDOS rom, the FDC can handle exotic 3inch floppy disk formats. RSX programs exist to get up to 208 KB of usable space per side.