Help Needed! BMS wiring

Hello, I have a battery pack made out of 20 1s 5ah cells from hobbyking. I have 2 questions. I am discharging them individually on my iMax B6 equivalent charger and the voltage is sagging .1V on a 1a draw. They are rated at 20C. Is this normal? Will there be this significant voltage sag when riding/accelerating? My second question is about BMS wiring. I created 2 packs of 10 batteries in series and then wired those packs in parallel. If I have just 1 BMS, how would I wire this? We can use this BMS for wiring purposes: Link to batteries:

Any 5ah 20C Lipo will have substantial voltage sag. Putting them in parallel will help some but still 20C is low even for a 10ah Battery.

5ah 20C means they are rated for 100a discharging

That is not a true equation.

In reality it’s more like this: AH x C / 3 5 x 20 / 3= 33a continuous current

Any amount of load will cause some voltage sag and the closer your load is to the true max the greater the sag will be