Hi, I found in the examples of fasm the hello world that uses invoke to call some functions.
How to call these functions in the nasm-like way?
(extern, import, stack, call)
Side-question: when using chars - what is faster - 'A' or 65d? Or there isn't a speed difference?

See the MSCOFF.ASM example.

Nope. There is no difference between A and 65.
Try this program:

And this:

Assemble with FASM and open with a text editor. (Make sure you're in ASCII/Text Mode) in both cases you'll see a A.
Next switch to decimal mode, in both cases you'll see a 65.
It's just a way how you represent them, like 0x0A is a hexadecimal while 10 is a decimal, however they are equal. So no difference.

Unless you are assembling things multiple times per second for every second 24/7 then I seriously doubt it makes any perceivable or important difference to assembly times. If you still really need to know which will be assembled faster then you can try a test for yourself and time it. But your speed results will likely be different from others with different CPU/mobo/RAM combinations.