Amd64 faster than i386?
What you don't want is modern Windows where it is 64-bit but you primarily run 32-bit applications through the WoW64 translation layer. Worst of both worlds (+ a translation layer) basically.
I believe Windows only switches from 32- to 64-bit code right before invoking syscalls. That should not have any measurable performance impact.
Yes, the main performance loss is with IA64 or ARM64 because it does actual emulation rather than executing instructions natively but there is still an overhead of around 2% for AMD64 when measured.
https://www.viva64.com/en/t/0056/
Before we go into fascinating but irrelevant speculation, maybe we should ask the OP what they really mean by the question?
(By they way, I'm using the gender-neutral pronoun, because I don't know whether the OP is a boy or a girl.)
Ever seen the french movie "La femme Nikita"?
But on topic - it depends. Pointers are 8 bytes then, but you have a lot more registers. I386 has how many free? Three?
Four general purpose plus two index registers plus EBP. Not counting, instruction, stack or flags registers.i386 has how many free? Three?