restrict and strict aliasing have to do with the same general concept, but aren't the same. They both have to do with allowing the compiler to optimize around assuming that writes to one pointer won't be visible while reading from another. As a concrete example, can the following branches be merged?

  void foo(/*restrict*/ bool* x, int* y) {
    if (*x) {
      printf("foo\n");
      *y = 0;
    }
    if (*x) {
      printf("bar\n");
    }
  }

Enabling strict aliasing is effectively an assertion that pointers of incompatible types will never point to the same data, so a write to y will never touch *x. restrict is an assertion to the compiler on that specific pointer that no other pointer aliases to it.

Not for char. Compiler always assumes non-restrict for char pointers and arrays, which is important to remember if you're ever operating on a RGB or YCbCr matrix or something.