the whole AP experience while holding the wheel and constantly trying to apply small amounts of resistance/torque (and still getting nagged every now and then) is now stressful enough that it’s no better FOR ME than to just use TACC.
If I’m putting so much work to get nags to go away, might as well steer myself on mostly straight highways.
That would suck. FOR ME the weight of my one arm holding the wheel is enough. I don't need to apply extra torque - just holding the wheel with one hand suffices. Left elbow on door windowsill, left hand on wheel around 9 o'clock. Or (either) arm in lap, hand resting on wheel at 5 or 7 o'clock. No need to exert turning pressure. Sometimes the latter position doesn't quite apply enough torque if I'm resting my hand too close to 6 o'clock. I hope this technique will work for you too.
21.9 has been fine for me. Showing the cars in other lanes get s shrug from me, as I can already see them by looking out the windshield! They don't appear in the most useful place - alongside. Many have pointed out the same thing so I hope an update will exploit the side cameras to reveal blind-spot vehicles.