I use the 300f4 with both the 1.4 and 2.0 TC. I have two pictures on my wall with the 2.0, an eagle perched a long-ways off and a Western Bluebird, also perched. I also have two shots with the 300f4 with no TC, a Great Kiskadee, perched and a couple of juvenile Redwing Blackbirds, in flight, squabbling over a perch.
Compared to several Nikon D-500/500pf shots, also on the wall, all the 300f4 shots look slightly sharper with the Great Kiskadee the best of the bunch (no TC)
All these shots were shot with an OM-1 mark 1 and printed on metal by Bay Photo 11x14 300dpi.
I just finished a trip with my new OM-1 mark 2 and shots birds-in-flight in ProCap 50 f/s, 300f4 no TC and the AF was amazing. I did not try a TC.
Tom