There is no perfect template.
If either or both are complete and utter shite, I agree: you won't be published. Because, if either or both are utter shite, it's because you can't write.
But if you're a good enough writer to have written a good book, your covering letter and synopsis won't be complete and utter shite. They just won't be.
So, you might not write the best covering letter or synopsis in the whole wide world and yes, it might even have the odd fugly bit in it, but, if you use your common sense and all the advice you've already read, you will be able to write a half decent one. If your writing is good enough, it will shine above any fugly bits.
If you write a half decent but imperfect covering letter and synopsis, and a GREAT book, it's most likely to be published.
If you write a splendiferously gorgeous covering letter and synopsis and a shite book, it won't be published.Because, it's all about the writing**.
So, go and make sure your book is great, yes?
** Oh, and having sexy legs, of course. Duh.