If you check "Fixed Text Angle", text will be oriented the same way as in original, no matter how the symbol is oriented. If you check "Allow geometry to mirror" or "Allow text to mirror" the geometry/text will be mirrored whenever symbol is mirrored and when checking "Allow text to flip", the text will be flipped whenever the symbol is flipped. In other words, let's say you are creating surface finish symbol. You want to specify machining with Ra=3.2 and by the drafting standards, this value should be oriented only in two ways. When symbol is rotated by 90 degrees text will also be rotated by 90 degrees if the Allow text to flip and Allow text to mirror are checked. If you rotate symbol by 180 degrees text will be oriented normally (i.e. horizontally from left to right). If you rotate the symbol by 270 degrees text will be rotated by 90 degrees.
If those options are not checked or if the Fixewd text angle option is selected text will be rotated with the symbol.
But, here's one more thing. For text to flip you should also set the drawing option flip_sym_rotated_text to yes.