Several battery connections independant of each other
The propper aproach is to add decoupling capacitors very close to the main devices which use significant energy. This will solve all your headakes which would come from inductance in transmission lines.

If you're not sure and want to go overboard, you can combine higher value electrolitic (100-1000uF) with lower value ceramic(1-10uF). The electrolitic is slower but stores more energy and the ceramic one is much faster to respond.