Which AP or Routerboard solution is best for IPhone 5?

what is your criteria for being "the best"?

any 1 chain RouterBOARD would suffice as phones cannot use more.

iPhone 5 supports 5GHz as well, so you can use that too. If all your home devices support 5GHz, it will work better than a 2GHz AP because of less interference in this range.

Yes, 5GHz is the point. What is the recommended model?

or I need to do assembly ( RouterBoard, 5GHz and 2.4GHz cards,pig tails, ANTs, case, power adapter) by myself?

At the moment, we don't have any indoor home AP with 5GHz already assembled. But you can order the RB711-5Hn in an indoor black case, with mounted antennas, any of our distributors should have it.

http://routerboard.com/RB711-5Hn
http://routerboard.com/CA411-711
http://routerboard.com/ACSWI

http://www.mikrotik.com/buy

Try this.. RB751U-2HnD

It has five Ethernet ports, one USB 2.0 port and a high power 2.4Ghz 1000mW 802.11b/g/n wireless AP with antennas built in.