Sounds like you may have had a whole-home energy audit done already -- including a blower door test? If not, I'd highly recommend it; I paid ~$500 for one a few years back which included thermal imaging, blower door tests, airflow measurements & calcs, current/draw measurements for all energy-consuming devices, thermal load calcs, etc. You may find better pricing even -- ours included a detached structure/office, and house is relatively large, multiple HVAC units/solar/pool/servers/etc...
In my case, I didn't end up with any super directly-actionable insights -- but it was still very well worth the money IMO. Even just to confirm that we weren't losing/"leaking" energy egregiously. The reality was, our household simply uses a lot of energy - hah.
I mention this all because, at the time, we were just about to replace our HVAC units & we had just installed solar + storage.
I'm located in Las Vegas -- summers are HOT (!) -- but our units (2x 5-ton Bosch heat pumps) can near-trivially keep us at 70F (or cooler), even on the hottest of days. I try to "push" the thermostats up a bit (we leverage a ToU energy plan), but there are days when the battle isn't worth having & the wife needs it at 69F -- and, even on the hottest Vegas days, we're able to hit it (can be expensive to do so, depending on time of day -- but is totally doable).
Edit to add -- Oversizing a system can very easily lead to issues; short-cycling, humidity control, etc. The ideal system will run nearly non-stop on "design" temperature days.
See if you can find any highly-rated Bosch installers locally; they'd likely be willing to "oversize" a system since the Bosch units are "variable capacity" (inverter-driven), which means you're less susceptible to hitting some of the common issues/concerns when oversizing traditional systems. Alternatively, the high-end variable-speed options from major brands are generally well-regarded though they can be extremely expensive (the price segmentation, and resultant value propositions, are bordering on dubious IMO).