Can I get a SEO penalty when using too many H2 tags (10+) on my article? (I must say that I don't look to spam or rank my content, I really need 10-20 H2 tags on my page)
There will be no negative impact. I used a holistic content strucuture for one of my pages and the Free Tools tell me there are too many H2 . But it doesn't matter in the end because there is an amount of Keywords which rank high. You should ask yourself if your content is strcutured and easy to read for users (and search engines as well).