RC Soarer
Just to help for the future mAh (milli amp hours) defines the capacity of a battery which indicates how long you can fly for before it will be exhausted. More mAh for longer duration but there is of course a down side. Batteries are heavy so the plane will use more power to fly so negating some of the duration benefit and the extra weight will make it a bit harder to fly.
The plan does suggest 800 to 1500 mAh 2s battery so 1300 is within the recommendation although towards the heavier end.
Selecting the best battery, motor and prop combination is not that simple as there are many interrelated variable and to a degree depends on your preference on how you want the plane to fly. It is therefore always best, at least initially, to keep within the recommendations.
+1 on this bit of info, I definitely second this. I tend to experiment(within the recommended limits) to find my preferred setup for each plane. As other have stated, mAh is basically your fuel, you capacity, how long your flight will last. Props are big, they can change the whole flight experience. I'm far from an expert yet, but you've got your diameter, pitch, and number of blades. More diameter and pitch is more torque but more power generally speaking. An increase in number of blades will give you more "excess thrust", especially at lower speeds, but is noticeably less "fuel efficient" than a two bladed, and can possibly limit top end speed a bit too. You definitely came to the right forum to ask questions though