As far as the battery question. The digital servos will drain that battery fairly quick. I have a 3D plane with the same servos plus 2 extra servos and I only get about 3 10-12 minute flights before I get nervous about battery usage.

Check out NOBS batteries, great prices and you can get a 1100mah pack or more that will keep you in the air for awhile.

If you dont have one already you will want ot get a Hobico voltwatch or something similar. Then before every flight you wont have any doubt how much juice you have left in your flight pack.

For your second plane you wont use much in the way of mixes, that will come later with a 3D plane or scale plane. However 2 aleron servos will give you better response.