MPPT controllers and cheap solar panels

Not really... Only two question that could do with a little further research--What is the 14 AWG cable runs length from panels to solar charge controller, and what is the run length and wire AWG from solar charge controller to battery bank.

Ideally, you would like 3% or less voltage (power) drop in the panel to controller wiring (with MPPT panels and several in series--Your system would work just fine with >>3% voltage drop, you just lose that power as wire heating instead of charging battery bank (I.e., 10% or ~5.4 volt drop, you would lose about 10% of your solar array output on a sunny/clear day with max battery charging (bulk charging).

On the wiring side from controller to battery bank, for a 12 volt battery bank you would want around 0.05 to 0.10 volt Max drop... This ensures that the controller is "seeing" the correct battery voltage and is charging optimally. Too much voltage drop, then the battery charging voltage ls lower, and reduced current flow, battery bank ncharges slower.

You could use a voltage drop calculator (one way wire length, working voltage, and max sustained current--Like this one):

https://www.calculator.net/voltage-drop-calculator.html

Other things... MPPT controllers (really any electronics) should be installed in an area with good cooling... Running hot, or lots of min/max temperature cycling causes shortens life for the electronics (and "hot" MPPT controllers can reduce current output to prevent overheating).

-Bill