Use of language and Words

This is just my point of view, so don't take what i say here as 'the thing to do.' Does anyone have trouble deciding the right sentences and word formation to use in a particular way? We can say things many different ways ... eg Tony left the house to go to the shops; Tony left the house to do some shopping. It was time for Tony to do some shopping.' Do how we say things in sentences matter to the storyline or to the reader if it says the same thing?
I learnt to spell certain words one way, then someone else tells me that that spelling is wrong. If 'lounge room' is two words, then why is bedroom and bathroom one word. I had learnt that 'lounge room' was one word and then find later someone had learnt it as two words. Also Australian spelling is different to the US English...such as behaviour, colour, but computer programs are often designed to the US spelling. Why does some words have a comma after it at the beginning of a sentence and others dont.. eg, But, So, Maybe, Then, However, also. I have noticed there is often differences as you read other author's grammer and language and they don't seem consistent with each other..even if they are from the same country. So,where does that leave you as the author to try to make the language and grammer perfect for your publisher when different publishers publish different things with the differences of grammer and language from different authors?

Doesnt the storyline mean anything to anyone anymore? Doesn't the content, the story, the message, the point of the entire book mean more than grammer and how things are said? I'm not talking about spelling here, but whether or not it reads properly if the sentence says the same?

I am in a fizz at the moment with caring more about how the sentence is said in my story than trying to create the story. I love dialogue but it's hard to create words with how the character is reacting around the dialogue. What words will have an impact? How do we decide what words will have that impact and what will impress the publisher or reader. One reader may like one word, while another thinks the word is the wrong word to use in that sentence. What does it matter? The point of the story is more important i think. What does everyone else think?
Roo