When I say a signature style, I don't mean the style of your actual signature. A signature style means a style that is so obviously consistent that a viewer doesn't even need to see a signature to know who the painter is. I sign mine on the back so the only way you'll see my actual signature is if you take a painting off the wall. Maybe you could do the same thing,sign them on the back?

For your actual signature, a signature doesn't have to be fancy, but it does have to be easily legible. You don't want people to struggle to read it. For a logo, that's another story. It's not REALLY 100% necessary. For me I knew I wanted to have products with my designs so, a logo helps with branding those. For a logo, if you don't already have some ideas, you might want to go on Fiver (or even on Steemit maybe there's someone?) and have some graphic designers who make logos all day show you some samples as ideas to give you inspiration. A logo should be pretty simple, and convey some idea about your brand/image.

For your question about titles, I wrote a post about that a while ago - here's the link to it! :) https://steemit.com/art/@adammillwardart/do-you-give-your-art-a-title-art-selling-tip