I missed explaining the differences why on some ships such as squid and galleon (sometimes fish) that I switch the positions of the wrench buff and spanner mallet buff engis
For galleon if you don't have a gunner then the spanner mallet buff is traditionally in the front position, and you should do this if you only have one buff engi. If there are two buff engis then the position of the spanner mallet buff is switched to the rear to give you better engine repairs at the cost of engine fire protection. Light engines have 300 HP while a wrench only repairs 120 so having a wrench buff on the rear will leave you with damaged engines. Having a spanner mallet also lets you bring moonshine which is great on galleon. The downside of having the wrench buff in the front is that you can't easily extinguish engine fires, but this isn't a big issue and the engines have plenty of health
For squid the tradeoff is more complicated. Having the spanner mallet buff on the right side gives you better repairs at the cost of bottom engine fires, while the wrench buff gives full autonomy on front at a cost of general repairs. The right engi has good access to the balloon if it breaks during engaging, and the default top position for the wrench buff engi gives you good access to fire control around the ship
When bringing the wrench buff on the right side you have no risk of fires, and if you're careful and not against a lot of disable (hwatchas hurt), the wrench is plenty to repair light damage on engines. Having the spanner mallet buff on the front can give you better general repairs while tanking because their default position is on the top deck which gives you easy access to the whole ship. The front will be vulnerable to fires and the main engi might need to use stamina to run to the front
There's a lot of variables when it comes to squid and there's many arguments for having spanner mallet buff on the front or side, but my quick reasoning for the spanner mallet buff on side is the better repairs and autonomy on front