How many more possibilities can you come up with? They are all "proper", but not necessarily the "best" designs. In fact, there are MANY ways it could be done properly, not just the ones you show, so it is a personal preference how you do it. The compass rose is immaterial in an isometric drawing, unless it is also "skewed" to show the pipe direction, The angles are mostly 30 and 60 degrees so there is no "southeast" diriection.