Deltarune, Rouxls Kaard Cosplay Help

I am new to Cosplay but me and my friends are going as Deltarune characters for halloween, and so I would like some help with the following questions:

1. Whats the differnce between Velvet and Uniform cloth?

2. To wear a wig should my hair be short?

3. Are custom sizes worth it?

All help is appreciated, Thank you/