My strong recommendation in response to your comment:
"I need to upgrade, but due to the cost / lifespan of these machines, I need to get it right!"
is to avoid AIO, buy a Mini or a Studio, and look to non-Apple display choices if a decently priced Apple display is unavailable in the size you want. Personally I have three Viewsonic 4K Pro displays but there are a plethora of great display choices out there, and everyone's needs vary.
My counsel is to avoid All-In-One ("AIO") computers.
• AIO forces one to replace everything if it becomes necessary to upgrade or replace the computer portion of the device.
• AIO forces one to replace everything if it becomes necessary to upgrade or replace the display portion of the device.
• AIO limits the user to the display choice(s) made available by the vendor (in this case Apple) at time of purchase. AIO excludes hundreds of other display alternatives from consideration, including Apple's standalone displays. Those hundreds of other display alternatives provide a huge range of pros/cons that may make for superior performance or value to a given individual setup than Apple's alternatives.
• AIO means one cannot change a workstation setup to something optimizing to a different display (e.g. larger) or to multiple displays.
• AIO means that when one has a dialed-in perfect workspace but wants to upgrade the computing by adding RAM or performance for whatever reasons, the computer upgrade may necessitate changing the already-dialed-in workstation to cope with whatever AIO Apple might have available at the time.