No AC concierge office per se at CDG T2A. Small team of 3, with usually 2 working at the same time. One of the team can generally be found on the bridge meeting the arrival of 870 and 880, the other working the desk in the MLL. Also usually present at gate for boarding.

The station lead agents are usually near the check-in area and then at the gate.

There is a small ticket office to the side of the check-in bank where you can bump into a concierge or a lead.

If arriving on LH, you will be at T1 and I don't see how/what the AC concierges can do to help you.

Public transport options are well described above by other posters, especially at the RATP site.