Re: academic writing
With apologies to my online colleagues who are in this world, I cannot suggest that "academic writing" is a style that anyone should strive for.
People who write in that style tend to be obscure and vague. It tends to feature astonishingly long, complex sentences that border on (and sometimes cross into) being impenetrable. It uses vocabulary that 98% of the people don't use in normal conversation. The goal often seems to me to show their cleverness, not to inform the reader. Yes, this is a stereotype, but I've read enough of it to know that it's a stereotype based on truth often enough.
I have nothing against formal writing.
To write well in a formal style, read many things written in a formal style.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.