the % size is in comparison to the actual plane hence a 50% model would represent 1/2 the size of the real airplane.

Control throw can be adjusted with a throw meter i like the ones that provide the % of throw from 0-70 ect

most people will recommend a neutral CG until you get the hang of 3d neutral being that while inverted it takes little to no pushing on the stick to fly inverted. a tail heavy plane will climb while inverted. with today's radio most people do not take off and land in 3d rates since they have flight modes or dual rates... its a learning process for you at this point a simulator would come in handy ....