Having some fun with the GOG version(1.2) and the OAW-GoG128Apr5.exe.
However I am having a difficult time hitting enemy aircraft. Any tips ?
I am finding it a lot more difficult compared to other sims.

Just to clarify if you press Ctrl-G and get the frame-rate in the top right corner then you have the GoG 1.28 exe loaded. If not you have the GoG 1.2 exe loaded.
In the latter there is no gun convergence for planes with wing mounted guns. This was one of the very first improvements added to 1.28, but to compensate for this the sizes of the hit bubbles was reduced.
I rarely shoot if the range is more that 1500 feet.

I do get the FPS counter when I hit Cntrl+G.

I am launching via the OAWSelector (Full) it shows "OAW Selector for GOG EAW 1.2" at the top left. Is this what I should be seeing ?

The main screen of the game shows version 1.2 in the bottom left corner.

I am I launching the game correctly ? I copied the GOG EAW game folder to another location and installed, then installed the OAW GOG 128 file (as per Patch for owners of the GoG release of EAW) thread.

Also, if I launch the game via GOG launcher, it shows v1.2 bottom left corner of the main menu.

So it is the 1.28 version with gun convergence.
I just flew it with the default ETO settings and shot down three Ju88As in six separate passes flying a Spit IX, aiming at engines from less that 1000 feet.
At that range you are taking risks

I am launching the game correctly then ?
Why does it not show v1.28 on the main menu ?

I will try flying closer. I'll try to be less trigger happy.