N4 is still (despite the name) part of TSMC’s 5nm process family and offers little to no performance/efficiency improvement over N5P.
N4 increases the number of EUV layers so the main improvements should be in cost and yield which would have been interesting to Apple, but N5P hit volume manufacturing earlier allowing Apple to ship the M2 earlier and with more capacity.
Waiting for N3 would have offered a considerable performance and efficiency boost but that’d realistically have delayed M2 to the first half of 2023.
N4 increases the number of EUV layers so the main improvements should be in cost and yield which would have been interesting to Apple, but N5P hit volume manufacturing earlier allowing Apple to ship the M2 earlier and with more capacity.
Waiting for N3 would have offered a considerable performance and efficiency boost but that’d realistically have delayed M2 to the first half of 2023.