I think the fans could as big as the 16"..and the free space to be filled with 30 more watt-hour lithium-polymer battery and bigger speakers ..who knows, i want to see the inside of both 14" and 16" with the m1 max..please man, show me the inside, i know you have them already...
Yes, the teardowns will help eventually.
Except not on the battery thing. The MBP 13" four port (Intel ) 58Whr ... MBP 14" 70Whr. There is only a 12Whr difference there. (about 20%). There is no movement on the MBP 16" ( somewhat max'ed out on carry on limitations. ) [ looking at it from 16" -> 14" battery transition probably is deceptive. ]
The MBP 14" is wider (~2%) and deeper (~2%) and heavier than the MBP it replaces , so Apple added a bit of thermal heft. ( if the twin fans are identical in both system then would be even. But there too.... the MBP 13" only had one fan. So more power once under heavily load. )
if Apple's pictures aren't a kluge the side vents on the 16" were adjusted to be about the same as the 14"
14"
16"
The 16" is deeper so that side slot could run longer. But the Mag Safe ( and HDMI ) port is shifted closer to the front.
( those side slots are coupled to the audio system so suggestive that they are the same. Same specs for audio so not sure why they would use different components over the same length).
Apple's air flow pictures suggest there is also an air inlet on the back. output and ingest near each other isn't the best thermal design guideline but 16" may be slightly better off if they are gapped wider apart. ( of course Apple is super eager not so show any substantive thermal vents because it is a "magical" system. So no pictures from behind. ).
The "stretch" from the 14 to the 16 is more so by the hinge where there is no battery. the thicker chassis is probably playing a bigger contribution to get the 16 a bigger battery. (wider also) . That non-battery area expansion is a bit suggestive that the fans are slightly bigger (and better) in the 16" than the 14". ( maybe some more funky bigger hinge stuff going on, but the fan/heatsinks are primarily in that zone. )