Same Anchor Text Everywhere is Good or Bad?

https://ahrefs.com/blog/anchor-text/
https://blog.kissmetrics.com/avoid-over-optimizing/

That's not quite what 'anchor text' means. It is important not to use the same keywords repeatedly. You'll notice that there are variety of "types" of backlinks. You want a mixture because that is how it would occur naturally, as people decide to link to your content. Over-optimization means that too much of one technique is used. The reliance on one technique over all others is how Google catches people (or thinks they've caught people) who are trying to game the system.

It's important to try to think as though you're the average Joe Schmo who decides to write about their favorite site or article. Each person will be a little different than the last.

I've not heard anything definitive from anyone. But I'd say something between 50-60% should be nofollow. That sounds like a lot but there are so many sites using nofollow these days that it's pretty realistic.

Likely, the repeated use of the same anchor text is the least of your problems. If all the links have the same text, it means that YOU placed the links, yourself, and there was no editorial decision being made by another website about whether they wanted to link to your site or not.

Google isn't stupid. They know that comment links, directory links, Web 2.0 links, social profile links, forum links can all be placed by someone who is not the site owner. That's why they are worthless. Links are part of their algorithm because it was meant to show that another site thought that your site was so good, THEY decided to link to it and send their site visitors away from their site to yours. Keep that in mind when you are trying to decide if something is a good or bad link - who made the decision to link to your site? If it was you, stop wasting your time.

I'll say it again (and again, and again, and again). If you can place a link yourself on a website owned by somebody else, it is almost always a very bad backlink. Using the same anchor text just makes it even more obvious and worse.

Stop trying to game the system; Google always catches up and buries your site. Instead, create something so great, other sites will WANT TO link to it. If you can't do that, I'm not sure why you even have a website.