Hi, like what Bryan said, it's better if you could avoid having redirects. Because of the extra step, redirects can affect your PageSpeed. We've always used redirects however - it's difficult to avoid - and it's very rarely flagged as a major issue when running the site in Google PageSpeed Insights and GTmetrix. The one thing we found that really has an impact on PageSpeed is a redirect chain, which should be avoided. This happens when a redirect goes to another redirect. Example: non-www redirected to a www version of the site, and then later on redirected again to an https www version. PageSpeed sites flag this as an issue, and so does Moz.

Hope this helps!

I was actually also looking for an answer to this and found threads way back 2013 with the same advice that keyword density doesn't matter. What I found using MozPro is that target keywords should be mentioned in the meta title, description, H1, URL (if possible), and at least once in the copy without breaking the keywords apart. I also found that mentioning a target keyword in a 500-word copy more than 15 times is flagged by Moz as stuffing. I just use these as a rough guide. When I'm feeling particularly worried that some keywords have been mentioned too much, I use a free keyword density analyser to see how many times they appeared and reduce if necessary (especially if the copy doesn't read too well because of too much repetitiveness). Hope this helps!