Regarding pain and 'more upright' I have two independent data points here.
1) I have significant osteoarthritis in both knees, get hyaluronic acid injections in both knees roughly 2x per year, and wear a custom brace on one knee (could well be both soon). It keeps the cycling related pain to a manageable level, but that is getting harder year by year. On every ride I do maybe 1 minute of hands free cycling just to maintain that skill. As soon as I sit up to go hands free I start to feel (low level) pain in my worst knee (right).
2) At the same time as the sitting up in #1 above, I also start to feel discomfort in my left hip.
Note that one pain is clearly sourced in my knee and the other is (I believe) now identified as being sourced in my back. No upright bikes for me!
dave