On offense, it depends if you are playing rush or pass. For both of these options there are formations which are recommended to use. In tight matches it could be a difference maker.
On defense, it also depends if you are awaiting pass or rush of your opponent. There are also some different options. The difference between 3-4 and 4-3 isn't much but the difference if you arrange a lot of DL (against rush) or a lot of DBs (against pass) could be big.
Nevertheless, in GI there isn't a right or a wrong way in creating formations. But there is some space for experiments