Power specifications.

This is not a big issue, you should be able to hear it but do not need it too loud. The impedance does not matter as long as any external speaker you use matches it.
Typical: 1.5Watts, 8 Ohms.

This is not a big issue, most legal sets will be around 0.8 Amps on receive and 1.6 Amps on transmit. This figure helps to decide how large a power supply you would need to run a mobile radio at home.

This was available on older UK sets, but is not usually important now.

Mobile standard: 13.2v DC.
Base radio UK standard: 240v AC.

See low power, above.

Legal USA maximum: 4 Watts carrier, 6 Watts peak AM, 12 Watts pep SSB.
Legal UK maximum: 4 Watts.