As long as I use default initialisation (allocatable, null pointer or null values) I see comparable performance for gfortran, ifort as well as ifx, no matter whether I use fixed size, allocatable or pointer arrays. So it all comes down to how fast a memory copy of a (default initialised) template can be performed I guess.
I once worried about performance penalty of default initialisation. However, if you really do something non-trivial with the values in the arrays, then the performed operations (including read from and write to memory) takes much more time then the default initialisation.
The only exception I remember was a very performance sensible simple and small hash map with fixed size (from which only a half or less was used as is usual with hash maps). Any size slightly too large became visible due to the necessary initialisation of the memory, which was mostly not used.