"John, if I understand things right, by having a few more turns on the new transformer (as in 123 vs 114 turn) , will decrease the flux density, but will have no negative effect on the transformer action itself, just increased copper losses,reduced winding room ?"
Close enough explanation. less steel, more turns more copper loss.
If we think the idle current needs to be lessened further, then more turns on the primary and secondary .
This means for the same inductance, the core will be less magnetized.. so less iron loss... but more copper loss.... but at idle, the copper loss will be virtually nil, and if we get the iron loss down, then our standby losses will be less.... a case of deciding where to stop really.
So, if you expect that the thing will run at low wattage most of the time, then more turns is the answer.. but if you think it will be running high loads for longer time periods, you may decide copper loss needs the attention.... like everything else.. it is all balancing plates in the air.
Addition.... if you want to tap, perhaps wire in the primary in two half winds , rather than center tap. That way in parallel, you have 24v full power, and series for 48v full power.
...............oztules