Content and style of H1 tag

[GeorgeKappa]

Hello once more, everyone.

My today's question is the following.

H1 tag is surely important.

Containing one for your keywords, seems of great importance too.

Any recommendations on the content of the H1 tag?

Should it look like a sentence and not plainly contain keywords, or not?

If your page does not have a big deal of text, if you had your (2-3 keywords -> 1 primary and 1-2 secondary) found in your title, title description and then, also in your H1 tag (or some of them at least) would the engines treat your page as spamming?

Additionally, there is a research that shows, that if the h1 tag is styled or unstyled, is of some importance.

research: http://cbutterworth.com/do-h1-tags-still-help-seo/

So, any suggestions on the h1 tag style?

Thank you all advance, again!