What is the best suitable software for assembly editing?

Hello, community!

I want to edit a Physical Product that is a Tool resource object created in 3DExperience. I want to rearrange some of its parts, modify lenght between parts just like the Smart Dimension tool in SOLIDWORKS, modify size of its components and edit connections between them like a "Add Mate" tool.

I would like to know what is/are the best software(s) to do this? I have heard of Assembly Design but I am not sure if that is the correct approach. Could someone help me?

Thank you in advance!
(I must warn that I am quite new to 3DExperience. Only been using it for 3 months. I might not understand some specific terms or not use the correct ones. Please be patient)

Design and Styling 
Assembly Design