Spartan has given you the best advice.

You could go for just a topper, let your sides grow longer and use some concealers to cover the thin patches, but in the end, this can be messy and time consuming and achieve a less than perfect result.

A 3/4 cap will give you a healthy looking head of hair, like in the pictures you've posted of how you'd want it to look.
There also will be less blending involved and colour matching will be easier.