Two effects: using too many conjunctions like Hemmingway and Cormac McCarthy. Or using none like Churchill or Lincoln. There are technical words for this. Bort knows them and so do you.

"I asked him with my eyes to ask again yes and then he
asked me would I yes to say yes my mountain flower and first I put my
arms around him yes and drew him down to me so he could feel my breasts
all perfume yes and his heart was going like mad and yes I said yes I will
Yes"
-james joyce

Kind of sleepy and emphatic.

"He was a bag of bones, a floppy doll, a broken stick, a maniac."
-kerouac

Staccato but maybe dismissive.

So is the mood determined by the syndetic coordination , or is the mood already there in the words and the author then decides the appropriate syntax.

If the author has a hardon/wide-on, the second one. Otherwise the first one.

Well Molly Bloom's soliloquy (the first) is all "wide on".

But these are both alternatives to the traditional comma, comma, conjunction.

To be honest, these days when I pick up a book and it has proper sentence structure, I assume it's a joke.

Herman Melville's pretty good at just writing loooooooooooong sentences that kind of run into each other. Was Kerouac on any of the drugs that give you a perma-horn?