There are usually two reasons why inswing is typical:
1. Often bath/bedrooms are accessed from a hall and having a door swing into the hall would create problems. You would have to keep the bath door closed at all times to prevent blocking the hall.
2. If the door swings out, the hinges are exposed on the outside. If you swing in, you never really see the hinges unless you are in the bathroom with the door closed. It makes for a cleaner look.
However, if you have a small bath/powder room, often you can only swing out or use a pocket door as there is just not enough room to swing in.
Sounds like you have it under control. Before you get too far, it would be a good idea to hang the door and temp install the vanity, toilet , etc. (or could use cardboard or similar to represent the size). See how it works. Try the door partially opened, try closing the door from different areas, see if the door is going to block access to anything. Although the door may clear everything, it is best to make sure that everything is functional and easy to get at with the door fully/partially opened. For instance, you may find the door clears the toilet, but you would have to stand on the toilet while closing since the door wouldn't clear you + the toilet.