Oh, and do I want to base the motor/speed controller's specs based off the motor's AMps, or the Battery's Ah?
You need to measure the motors stall current, make sure the motor controller can supply it, and then buy batteries that can supply a peak of the stall current but will also last for a 'reasonable' time when just supplying the 'average' current'
I am about to purchase two 12V 18AH sealed lead acid batteries for two 24v Wheelchair motors,
12V batteries for 24v motors. So the motors will run with less torque. Which may be ok - depends on your motors and what you want. If you believe that your average current is 10Amps then they will last for 18/10 hours (ie 1.8 hours).
And if I were to base the motor driver specs off of the motors, would I take each individual motor's amp and add them or keep them for the driver. For example, I have two 24v motors /w 10A, do I want a 10A motor driver, or a 20A motor driver.
You need to check the controller datasheets. Look for one that provides 10A per channel.
Would a better bet just getting 8 20A relays?
But then you would have no speed control. Just fwd, backwards, stop.