Pretty simple:
- OCS/ECS machines run on a bus frequency of 7.16 Mhz, bus width is 16 bit, including Zorro II. The 68000 can use every other cycle to access the bus, so that's 7 MB/s.
- Turboboards have their own (fastmem) bus, so bandwidth varies.
- The A3k's chipmem can be accessed in 32 bit cycles (only) by the CPU, so that doubles bandwidth.
- AGA machines have 4x the bandwidth (double clock rate and 32 bit access)
- AGA blitters can operate in 16 bit only
- Zorro III is an asynchronous bus, so it's not possible to give a specific bandwidth. In A3k/A4k it maxes at ~20 MB/s (AFAIK).