I have noticed that not all properties "charge" the same amount for points. In other words, Property A might charge M dollars for 10,000 points while Property B will charge N dollars for 10,000 points. The moral of the story is to investigate how to minimize the number of dollars by varying which properties are all points, which are a mixture, and which are all dollars.

My recollection from a few years ago (perhaps 2018) is that buying more points (say, 25,000 rather than 10,000) at a property sometimes results in a lower cost per point. It's another variable that will consume more time as you explore options.

My other recollection is that there is no practical way to use you spouse's points on the same reservation where you use your points.

If you will stay four nights at any property, you should consider getting an IHG credit card from Chase that will provide a "fourth night free" benefit.

Another recollection is that if you buy points using a Points + Cash rate, the points that you immediately purchase do not count as spend at an IHG property. Please, someone correct me if I'm misremembering.

Good luck.