As I’ve been mentioning many times thumbnail + title is the most important thing for successful YouTube channel, there are obviously vaguely rare exceptions, but chances for that you are one are rather slim, so stick to the rules and invest some time in it!

Program

You need decent graphical program of course, so there is rather simplified chart

Professional

Affinity Photo > Photoshop

Web

Photopea > Canva

FOSS

Krita > Gimp