Battery Connection Setup

I am working on an electronic only setup and have a question. I have (2) 27 and (2) 29 series batteries that I want to run 2 parallel banks and in turn bridge the 2 banks in series for a 24 volt TM. Wanted opinions on should I keep the parallel banks like in kind or should I run one of each in parallel. From the best I can research both sets of batteries are pretty close on specs. Eventually, I will purchase 2 more of the 27's and this will no be an issue.

Second question. With this setup I will be using (2) 12 volt chargers. Positive 1 and negative 2 post connected to the charger. At what amp charge does it become necessary to run a voltage drop balancing wiring instead of connecting directly to the battery terminals? How long/short does the balancing wire need to be to work effectively?