In order to compete with native-speaker researchers, non-native writers of English, in particular, do need to master English syntax in a way that enables them to produce meaningful and accurate research writing.
Any writer, native speaker or not, needs to make excellent use the elements you list. Not all native speakers are good at these things. :-)
The reason this is necessary is that the language must be easy to read and engage the reader in order to be successful, so elevated language use is best.
Of course they do. There still is the question whether they could and should strive for perfection, after all, scientists from the field of history, mathematics, or psychology are no linguists and it seems natural that they focus on their respective fields. Also the reader has a keen interest in just those special fields and not in English linguistics or literature (unless that is exactly the field said scientists are working on). But as with all scientific writing there appear to be some key elements one has to keep in mind:
Goal and meaning
"message" of the text has to come across
author has to master English to a degree that enables him to express his ideas clearly
reader has to be able to follow the trail of thought
attention and focus of the reader should not be disturbed by a writing style and syntax that is unusual to an extend that the reader has to focus too much on what the writer tries to say, driving his mind away from the ideas the author tries to bring across
These points are of importance in any language. There are always scientists who try to "pimp" their essays and load them with a lot of latin words to make them appear more intellectual. They clearly do not keep the best interest of the reader in mind. Whats' important: you got a message, you got content, your reader has to understand the idea and what you are trying to say. Weird phrasing ad syntax easily get in the way of that. This does not mean that you have to try to become a second Shakespeare or Robert Frost, but you have to be as clear as possible. If you achieved that, do not mind little linguistic shortcomings. English is spoken all over the world and the native reader is used to it not following the Oxford standard always.
Every good writer—and not just non-native ones—should have the ability to play with words and sentence construction to bring out the best in an article. The language skills required for composing highly technical prose come with deliberate practice—and not as a matter of course—even for native speakers of a language.
See more on: https://www.researchgate.net/institution/Peerwith_Connecting_Experts/post/5bf52e220f95f19d9f3ce50a_For_clients_and_experts_Why_Peerwith
Of course! every good writer should be conscious of the way to attract and sustain the interest of his readers. Syntax, Words, Phontetics, Morphology, Rhetoric give many opportunities to do so. No need to be linguist to have those ways at one's hand. Just pay attention to the rythm of sentences and clauses.