How much power is generated by a Ram Air Turbine (RAT)?
According to the Flight Crew Operations Manual of the Boeing 777:
Hydraulics

The RAT, when deployed, provides hydraulic power only to the primary
flight control components connected to the center hydraulic system.


Which leaves out:

Nose gear
Main gear
Steering
Brakes
Flaps
Thrust reversers

Electric
The RAT powers both C1 TRU and C2 TRU, which powers the captain's and first officer's flight instruments, respectively.
The RAT can supply electrical and hydraulic power simultaneously. However, if the RAT is unable to maintain its RPM, the electrical load is shed and provided by the main battery, until RPM is satisfactory.