Depends.

Sometimes it's pinky on the CTRL and index on AZXCV ie the hand lower/closer to me.

Sometimes it's pushing CTRL with an edge of the hand and with the fingers on the ASDF to press AFRCVB.

Sometimes it's my hand on ESDF with run around in Zandronum and pushing CTRL with an edge of the hand to invoke 'invuseall'.

The main driver for moving SHIFT to CAPSLOCK is what SHIFT is used way more common than CTRL and with my big hands it gets quite uncomfortable for my pinky to used too much in an awkward shrimp mode.

NB on a non-laptop keyboards I flip both Windows/Super keycaps upside-down, helps a bit.