Hope this is the correct place to ask. The FFP and CC program section seemed to direct me to the specific mileage program section for something like this.

A little background...
Home airport is Boston-Logan, main flight I take is the BOS-NRT direct. As I only fly this once a year/once every two years, I know I am not frequent enough to earn miles for status nor reward tickets.
As JMB miles are valid for 36 months, I was looking at their rewards and seeing the 30,000 mile one-way upgrade to Business class may be within reach as I will earn 14740 miles according to their calculator for the above roundtrip. Currently a JMB member with some miles on it and a JALCard USA holder, was looking around for a program to generate additional mileage/points.

Seeing the SPG card from Amex seems to be the best deal as it transfers directly to JMB if I can meet the spend requirements for the bonus. Though when I was researching this, I read about some Amex and Citi cards that transfer to Asia Miles... I am understanding correctly this is a separate program but can be redeemed on JAL?
Since I do not normally fly on partners like AA or BA I feel like I am a little limited, but this seems to be about what to expect if I'm flying JAL only?