This board style is common in Australia. Miniature Circuit Breakers (MCB’s) are 17.5mm wide for single pole and typically 16A, 20A or 32A. I agree that the offered CTs seem to be undesirable for MCB installations.
Is there a CT which can fit into this 17.5mm space? I think split core is less important than being able to fit into a single MCB width.
There is lots of space in the box itself but it seems that the installing electrician has been ‘too neat’. It looks like the load cables run behind the breakers.
If there is ‘extra’ cable loose above/below the box then great you could pull that through, and remake the connections with longer wires for the CTs sitting in the bottom left corner and top left corner.
If that isn’t possible then crimping extensions to the live wires to give space for the CTs would be the way I would go.
A third possibility would be to fit an intermediate box below the main one, Break the cables there and install the CT’s in that box. Wago have a number of kits that are designed for this purpose (don’t know if they are sold in Australia or would be compliant with Australian Standards if they were)
This panel looks very much like a US breaker panel. There appear to be 12 neutral wires running from the neutral bus on the right, under the central buss, and into each of the individual breakers on the left. They don’t appear to be labelled, but if they can be identified as to their corresponding circuits, you could easily place 50A split-core CTs on them to measure each circuit.