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Every serious race engine that I know of uses the biggest bore allowed by the rules. Most rule limited racing has a bore size limit (or a bore spacing limit) for this very reason. The stroke is just there to get the displacement allowed by the rules.

If the displacement is unlimited then the big buck guys go with the biggest bore and the biggest stroke that they can buy.

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I disagree..
99% of the people out there the block is a limiting factor on bore size. They run the largest bores they can without going to thin.. very, very small % or racers are running class rules. 85-90% are your average bracket racer in the real world.... And they are plenty serious too..
As for stroke, I will say head volume plays a much greater role in peak RPM.
Build a decent stock 440 with stock stroke and some compression with stock heads see what it will RPM.....
I know about 6K with a decent solid flat tappet cam say a MP 590...
Take the same engine and throw a set of well prep'd 440-1's and see what it will want to turn?
More, a bunch more...
Now build the same engine and test with a 4.15 stroke crank, or even a 4.25 crank...
RPM wont be much diff than the same 440 with the same heads etc.
Your heads and cam/valve train dictates peak RPM.
I turn a 4.5 stroke 8K with a set of 440-1's. I know a 4.15 stroke will go that too. The 4.5 stoke has way way more cycles per minute, which wears out parts though.
Im am not so sure a 4.5 stroke is faster or makes more power than a similar engine with a 4.25 stroke...
I truly believe after 4.25 + in stroke it just doesnt impact a engine performance wise as much as overall parts selection.... I know this to be true, despite what the text book racers may think.