My personal feeling is anything towards a westerly direction might cause more disadvantage in terms of heating than benefit in terms of cross ventilation. Bear in mind people aired their houses for a long time before open plan and airconditioning and multiple windows in each room became a thing, when houses were just a series of rooms with a door and a window. So a second window for that purpose might not be necessary. If you have a view you want to enjoy, vertical windows make sense, but the greater exposure to sun needs to be addressed by provision of external shade.

Which direction does the other window face?

Do you typically keep the door closed blocking the ability for cross ventilation from elsewhere?

From which direction do your prevailing cool breezes come from?

Is an external shade structure or fitting within the bounds of your budget/space/aesthetics?

Wow, so much to consider! I actually don't know the answers to many. We are have double glazing windows and we will have ducted air con. I guess our door is mostly closed. The cool breeze comes from the south west. Our master windows are facing the following direction.

window orientation is important but please describe your local climate

Oh yes, climate. If you are putting in a pool presumably mild to warm, so summer cooling is more important than winter heaing?

You said the window/s face NNW and the compass appears to show I think WNW? Are you maybe talking about the same windows. Will there be windows on one wall or two walls?

Yes, we live in Perth, hot summers, mild winters. Average 18 to 20c day winter temps. Can be cool overnight at times. I redid the orientation on the compass from the actual bedroom windows. Thank you.

Without context I'm not really understadning the compass.

Do you have a floorplan you can post?

Will there be one wall with windows or two?

You have a bedroom and used the compass to find the orientation but you don't have the windows yet, is it a reno?

I have seen bedrooms with only vertical windows, but I have not usually seen master bedrooms with a highlight window and no other window in the room.

Once it is drawn I will post. To be honest I don't think I'm using the compass correctly. You are right though...I don't think I've seen a master with a highlight. ...I'm thinking perhaps floor to ceiling verticals starting from the outside of bedside tables. We will have 33course ceilings. Or perhaps start the vertical windows above the bedside tables. We will have only one wall of windows which will be directed at the backyard with pool.

If those are your only windows, and if you have a nice view too, do verticals.

But if they get summer sun, especially in the afternoon, which they will if they face somewhat west, provide some form of external shade to reduce heat.

Think about how you would do curtains. Unless you r a blind person. But equally what are you seeing out of the windows?

Also think about the aesthetic from the outside!