unless you change the piping you wont have any back rpessure issues
that type of muffler will be loud get an oval one to reduce the resonace if you want a quieter ride with a bit more grunt
My cousin has a wide oval as but a dual tip and it is loud and annoying when driving a complete difference compared to my muffler with new piping from the resonator back and an oval muffler and tip
your choice
and jack ,nice way to make a blanket statment
thousands of civics have a round tanabe style muffler with no chopped springs , very few idiots drive with chopped springs, not because they drive a civc but because they are just idiots