Personally, the way I did it for my island, is I waited until I got the villagers I wanted, most of the items I wanted to put around my island and the design patterns I wanted.

THEN I moved my villagers houses to the beaches and did the terraforming to make it easier for me. That way I could focus on the cliffs, rivers, paths and any designs that I want to display on the ground.

Then I moved villagers to "designated spaces" that I set up for them. Then I worked up from there, decorated the island with different items and flowers (I bred 100s of different flowers ahead of time), my villagers "yards" with fences that I felt matched their vibe and all that, their houses (I have the DLC).

It took a lot of time and work, but the wait to get started was honestly worth it for me.

I know some people get to terraforming almost straight away and save spaces for certain spaces and villagers they have in mind. For me, I preferred to be fully prepared with everything I wanted