DC/DC buck/bost mudules vs LM317 comparing for Bench power supply circuit
To answer you main question about LM317 performance.
The current vs voltage output chart for LM317 is much worse than for the switching module.  You're limited to less-than or equal the input current at all voltages,  and are limited to less if it starts to overheat because the heatsink is too small. (so the slope may actually be backwards compared to what you posted.  and all the numbers are worse)
some comments on your drawing.
You have drawn a &quot;boost converter&quot; where you probably want a buck converter
If the current is less than 10A you can use a voltmeter-ammeter module that has an integrated shunt.
you may have to place the shunt in the negative side of the output
If you connect the ground end of the voltage setting potentiometer to a small voltage instead of to ground you will be able to adjust the voltage down to zero. (eg use a resistive divider off the 12V supply to make 1.5V )