I think part of it depends on what your aim is here. If you want to minimize the number of connections you have (and the chances you are left stranded at an airport) there is frankly only one option here: Sydney to DFW on QF, followed by a 4 hour layover at DFW and then a short hop onwards on AA to SDF:
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In terms of aircraft I'll take a 787 over an A330 any day of the week. The 787 has a number of cabin comforts that the A330 simply doesn't have including adjustable dimming of the windows and added humidity in the cabin. One thing I'm less aware are the quality of the lounges at DFW particularly for OWEs. For instance you should have access to the AA Flagship lounge as a QF Platinum as you're travelling on AA to SDF. But are there showers there? Certainly after such a long haul "domestic" hop to the US, the first thing that comes to my mind is having a shower, especially in this COVID environment we face.
As for immigration at DFW - I can't comment on that as I haven't had the opportunity to try the GlobalEntry kiosk there nor the TSA Pre-check security either!
-RooFlyer88