Hello!

I have a YouTube channel and I can prove that the thumbnail is very important to capture the attention of users, both subscribers and search results.

It depends a lot on the type of content you upload, but you should ALWAYS create thumbnails, because if you are solving something, the so-called How to... must convince the user that if they click on it, they will know how to do it.

You can measure whether they work or not, thanks to the statistics offered by YouTube Studio, in Coverage, Click-through rate of impressions. The best thing is to try several strategies and compare them with the advanced visualization, discovering which one works best for you, and once you have it, keep it and improve it little by little.

I use CANVA, which with the free version, so far is enough for me after my 50 published videos...In addition, you can copy-paste so you take advantage of the work already done and modify little...

I just uploaded a video that I hope will help you create yours.