There is a set of parameters that flakes perform best in.
Chambers around 18-19 mm. wide and equally deep are ideal. That translates into (by modern standards) smallish apples, bent bulldogs, princes & the like. With Virginia flakes, you're looking at about a one-hour smoke here.
Bigger may or may not be better in Mumbles' everything-is-relative view. But bigger, with flakes, certainly means longer elapsed times, and wider = much greater difficulty with keeping your flakes from burning down the center, leaving the periphery just toasted.
Having the chamber deeper than it is wide can prolong a nice time, but you can more easily run into difficulties with moisture in them.
The fact that you're asking pretty much implies you'd be best off starting with a shape & size that's easiest to manage. Which is what experience, and the example of the golden age British pipemakers has pretty conclusively established.
Once you've got the basics down, it's easy to go from there, because you've only got one variable at a time to play with.
Then, if you want to put whipped cream on your scrambled eggs, go for it.
FWIW
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