Crowdfunding kickstarter sale copy and voiceover script

Num. of words: depends Topic: product screenplay voiceover script Tone: Formal/Professional Extensive research needed: yes Extra notes: just learn that voiceover should be done before filming? so is it correct to get written voiceover first and sale copy of product page? to let budget low the correct flow should be: voiceover screenplay filming edit? want to find a talent to write for my several product, led mirror , gaming mouse etc for voiceover script and product sale copy for crowdfunding page. here is one of my product https://www.amazon.com/Mirrors/dp/B01CHOWTDW