As promised the wiring I used to fit a Sotabeams CW filter into the uBitX, mine is a Version 5 board.
J1 is the connection on the board and a yellow wire comes from that and is soldered to the input of the volume control.
J2 has an orange wire that goes from the wiper of the volume control back to the board alongside J1 and the yellow wire. The third terminal on the volume control goes to ground connection.
With the switch up the yellow wire from J1 on the board goes to 2 on the switch and 1 on the switch takes it to the input of the volume control - so the filter is bypassed.
When the switch is down then 2 on the switch is connected to 3 and the signal is then taken to the input of the filter. The signal passes through the filter and returns to 5 on the switch which is also connected to 6 and the filtered signal is returned to the input of the volume control.
The audio level is controlled by the volume control whether the filter is by-passed or inline. When the filter is switched in it is in wide CW mode. A second switch is needed to switch a terminal on the filter to ground and that gives the narrow CW mode but I have left that off the drawing.
I don't see why you can't fit the AGC into the yellow wire leading to the input of the volume control and then put the filter between it and the input. I don't have AGC (yet) but this wiring works perfectly for me.
Hope that helps,