Can I recharge 12V batteries individually while why are attached in series?
Series is risk especially for mismatched batteries. In order to prevent thermal runaway of a weak cell each cell must be matched within 3%.  I suggest you stick with parallel operation but ensure they are matched in model and age and consider a boost regulator that prevents undervoltage on PV panel by voltage feedback and overvoltage by voltage feedback. and let it run anywhere around 16 to 18V. THat will be fine for the DC-DC step-down ocnverters for the laptop cells and MOBO DC-DC converters. How you do it depends on your power budgets.