I am an editor on one of the journals you have mentioned in the post. The similarity percentage number does not matter to us as much as the detailed plagiarism report. If you have 30% similarity, and out of that 20% is in your citations and footnotes (which necessarily have to follow a standard format), then we disregard that percentage.
It is an evaluation of the whole paper to figure out what you have taken from where, what you have cited, are the arguments merely paraphrased (hence plagiarized, but not similar) from existing sources, have paragraphs been copied directly, etc.

For selected pieces, we open each citation to read it and check that the cited content is indeed there and then we also do general literature checks to ensure that the submission is novel. Subject to these conditions (and other conditions of peer reviewer approval, comparative quality with other submissions, etc.) the piece proceeds for publication.

But to answer in short - a particular percentage of similarity doesn't matter. What is showing up as similar and whether it is to defraud us into thinking that it is your idea is what matters.

UGC as usual in a display of ineptitude has confused plagiarism with similarity, just like a host of ignorant faculty members and NLU admins do. Similarity will be there even when I actually cite or quote my source, but that would not count as plagiarism. Of course, a journal may not select a paper if it lacks originality and mostly borrows from other sources, but it cannot do so on the ground of plagiarism if the sources have been properly cited.

Hi , I was hoping to get insights from editorial board of top law reviews in India like NLSIR , NALSAR Student Law Review (who folllow a double peer blind review process ) to name a few on the "acceptable" plagiarism limit while considering submissions for the law review. The UGC (Promotion of Academic Integrity and Prevention of Plagiarism in Higher Educational Institutions) Regulations, 2018 put it into 3 levels -

8. Levels of Plagiarism
Plagiarism would be quantified into following levels in ascending order of severity for the purpose of its definition:
i. Level 0: Similarities upto 10% - Minor similarities, no penalty
ii. Level 1: Similarities above 10% to 40%
iii. Level 2: Similarities above 40% to 60%
iv. Level 3: Similarities above 60%

So do law reviews follow the UGC limits and consider papers only below 10% or are even stricter ??

Any insights will be helpful for all law students wanting to publish academic articles in prominent law reviews!