Can I increase from 32 bits(default) to 64 bits in APB, for data bus width?
No, the protocol only supports 8, 16 or 32-bit data buses.
The original APB protocol was intended to support simple relatively low bandwidth requiring peripherals, so wide data paths or complex controls were not required or desired, with components requiring higher bandwidth functionaility expected to be implemented on systems buses such as AHB or AXI where wider data buses are supported.
Over the years the APB protocol has become a bit more complex with the addition of wait states, error responses, write strobes and protection types, but we are still looking at supporting peripherals with narrower data bus requirements, so no extensions of data bus widths.