Yep, either one of those thicknesses will work. From the looks of the video, he had a vac table but didn't use it. If you wanted to make your visor like he did, I don't even think you would need a vac table. Just have the buck on a stable surface, have the heated plastic form around the visor, and use a heat gun to form the rest of the visor. If he had used his vac table and heated the plastic correctly, then he wouldn't need to use a heat gun. Since he used a heat gun, bubbles formed on his plastic visor which he mentions. (I hope this doesn't look like I'm harping on him :unsure. I just think the visor could have came out better had he used his vac table.) From what I hear, vacuum forming isn't exactly easy. Experience really plays a huge part.
Regardless, I really think you should make a table. Having a vac table will achieve a more crisp looking visor. As long as you have some carpentry skills, making a vac table is not very difficult. Plus, whenever you make another helmet you can always get nicely formed visors. I'm basing my vac table off of
XRobots Vacuum Forming Table. I'm hoping to get similar results to
Justinian117.
Best of luck on your visor!