"How important is the detail?" The more the better but you need to start somewhere.
James Dyson, the vacuum cleaner guy, started with cardboard and duct tape.
"Also does the material used, and the skill level of the builder effect the manufacturing process?
Prototyping is an iterative process. You learn and refine along the way. I like to prove out the concept with chipboard, the thin cardboard on the back of a note pad.
Then I may move to more rigid materials like plastic or wood. It depends on your skill level and tools.
Then I may decide to use an SLA or 3-D printed model. Small parts start around $150 so I like to be sure that the design is solid before I pay for this.
After the rapid prototype, you may decide to get a prototype tool made. For an injection mold, figure $2,000 and up. The good thing is if the design is solid, you cam make up to 50,000 parts. The downside is that the cost per part will be higher because the proto tool is not set up for high volume production.
The part can look just like and perform as well as a production part.
Also does the material used, and the skill level of the builder effect the manufacturing process?