There really are no "regulations". There are standards. I'm not aware of regs any that cover that. Short straight and as minimal lengths of fuel
line would be the best solution. Extra connections, valves, and anything not straight is an invitation to air leaks
My own opinion is more tanks is worse than fewer tanks. It's not easy to make one big huge monster tank so splitting it up helps weight distribution. I'm not a believer in "day" tanks either. It all ends up some place. On a 40 ft boat you have no problem with too much fuel because you can haul enough to hit the radar screen
Complicated fuel systems with small tanks (less than 1000 liters) are money
down a rat hole and complexity you don't need or want. You area sail boat that uses an auxiliary engine
Trace an air leak once and you can understand why. You are one person without a crew to send off chasing such details.