What size service do you have?

If all you need is a couple of lights and some general use receptacles, then that only needs one circuit.
Then run another dedicated circuit for the air conditioner.
A subpanel seems like overkill unless you are planning on future expansion.

Think that my main is 100.
The main reason for going with a sub is ease of installation.With the sub in the attic I reach all four walls from above, then just drop down between the planks (nice gaps) to the outlets and the switch.

Thanks for the comments.

"With the sub in the attic"

You have head clearance in the attic 30 inches wide and 36 inches deep (form the front of the panel)??

A sub requires the same clearance as any other panel, think abut a refrigerator box volume in front of the panel.

Run 2 12-3 romex into the attic and terminate them each into their own 4" sq box. From there, you can do about whatever you want.

You can branch from a junction box. A subpanel is overkill and wouldn't ease your installation at all. It would do the opposite.

For rewiring from an attic, I use 4 11/16 boxes to accommodate more cables.