Power output of a transformer with many secondary coils, each coil of turn exactly equal to that of primary?
If all coils have the same number of turns, they will all (theoretically) have the same voltage - 100VAC in on any coil, and all others will output 100 VAC.
The total current from all secondary coils will theoretically equal the current in the primary coil. (There will be some losses in the transformer, so the input current will be slighty greater than the total output current.)
The currents in the individual secondaries will depend on the loads connected to each secondary winding. One secondary could deliver 10 amps, another 5 amps, five delivering 1 amp each, and the remaining 3 secondaries not delivering any current.