Seems to me you are mixing up what you “want” with what you “need”. Your choice if frame should be 100% driven by the needs of your back.
I have just been through all this. Buying endless beautiful bikes that I just cannot ride. Turns out I broke my back when I was 17 and never knew, just a vertibrae. This meant my neck C1 also had to be wrong to compensate and put my head back to straight up and down.
I simply just had to get away from arse up head down and sit upright with bars level with saddle.
I bought a frame with a short top tube and very high stack. That is a frame designed for drops but used with curved flats, and very high stack allowing for 100mm travel. Ok you say its an MTB but who cares, I built it up to suit me and my back.
The result is I have a bike I can ride every day for the first time in many years. it also has a Thudbuster and titanium Brooke’s so no jarring at all for my back.
It is just so wonderful to be able to ride again, no sore neck, no sore thigh, no lower back pain.
So my advice is concentrate on what your back needs, what ever that is, that’s what you have to do.
Brian