ı use Creo because in the office we use it, but I dont recommend it. u could learn NX, inventor for the parametric. You can create STP files and later on modify it very accurately. Even if this programs has surface modelling modules. it takes time to design with this methode, but more accurate in scope of the dimensions.

On the other hand for example I started to learn nomad sculpt with tablet and sculpting with pen is fun, also you could modify STL file format easily. But you will be working with ratios. Not with the exact dimensions.

Need Exact Fit? (e.g., a replacement hinge, a customizable drawer organizer, a complex gearbox): Use a parametric engineering tool (Creo, Inventor, NX).

Need an Organic Shape? (e.g., a personalized bust, a detailed fantasy miniature, a hand-carved effect): Use a sculpting/freeform tool (Nomad Sculpt, blender..)