Can I use two single ended output transformers in a push-pull circuit and then parallel the outputs?
What you’re making really IS two class A output stages run in parallel. With no magnetic coupling between the two half-primaries, there is no interaction on the secondaries, either. You have to run them Class A to keep from having distortion because they really are separate amplifiers. It’s not clear what happens if/when you try to use feedback from the secondary into the (presumably)common driver stage. On the secondaries, you have two 8 ohm outputs that you can connect in series to drive either two 8 ohm loads separately or one 16 ohm by placing the secondaries in series; the resulting power capability, given that you get the rest of the circuit right, is the sum from each transformer, or about 2X the power of each Class A amp by itself. Note that this is far less than you’d get by using a proper push-pull OT and driving it in Class AB, probably ¼ the power. If you try to parallel the two, you can get some interesting and possibly disturbing results. If the transformers really
