This is called buying off-plan.
Usually it means you get a better price as selling is slow and there is a long wait for your plot to be built.
If house prices go up whilst the home is being built you can be quids in. If they go down, you may move in with negative equity.
You may find my article on
Buying Off-Plan helpful.
As far as the home and value for money is concerned, you will need to assess the price per square metre of floor area and weigh this up with the benefits the differences would have to your own needs.
Before buying a Walker Homes Scotland new home you really need to read the posts others who did have on this forum.
Use the forum search bar and search "Walker"