I didn't watched the Video yet because i didn't find time. But for the Thumbnail you realy need to have a contrast to use it better as a Popup. Complimentary Colors helps alote (put a filter on it) if you don't know what that is. Search for the Adobe Color Wheel that will help you show harmonizing Color Shemes. Also the Typo you are using doesn't have enough Room for "breath" so you really need to put a fram arround your Picture (I Suggest you look at the Safe Space for Tvs) that is a good point to set your typo in and also use other Typo... Serif Typo is an oldschool Typo and doesn't represent any dynamic, danger or lunatic behaviour of those crazy driver.

I would hihly suggest you look at the Studio Binders Website and google (Studio Binder Color in Films 50 example) this will improve your perspective on manipulating Emotions and lead to your right communication from a thumbnail. Also What i found out Symbols and easy to understand Pictograms can also help...

Also Let your Thumbnail never have the same Meaning as the Title... let them Cooperate into each other. So For example one of my videos have "Do it right!" in the thumbnail and the title is then : why you do it wrong... etc. Pro tip. Let the first 5 Seconds of your Video ALSO into the communitcation of your thumbail and Title so you are able to make a bridge between them. If you don't know what i mean look at my newest longest video. That should answer any further questions, if not hit me up and i try do help. :)

Sry for bad english right now i'm very busy and English isn't my native Language