I have done many tests for the last 12-16 months. 2 websites in the same niche, different fresh domains, same wordpress setup, same articles (manually rewritten with 100% unique content). Every website has 25 articles.
First Website:
- 1 PBN link to root Domain
- 1 PBN link to an Article
Second Website:
- 5 high authority do-follow profile links to root Domain
- 5 high authority... links to an Article
Guess what? ;-) Second Website has a higher crawling rate, all 25 articles are indexed within 14 days and ranked good after 21 days. First website needed over 20 days for indexing, lower crawling rate, and only the article with PBN link is well ranked, other Articles are between serp position 60-90.
My conclusion: high authority do-follow links have a lot of impact when done right.
Please note: all my tests were done with very low competition keywords to see possible effects.