Query; are the Rakata Ruins (big starship hook decoration bought from the vendor on the fleet who sells all the Rakata decos) purely visual and tempting or is there actually a way to climb up to the top of those floating platforms?

I'm not sure about the climbability, but I will warn you that if you put a decoration in the path your character takes during a first-visit cutscene, your character will walk through it as if it's not there during the cutscene.

You can climb them to a point

You can totally climb on it. We did it in 3 today.