Pads make a huge difference.
The results are easily seen in measurements and at levels that will most definitely be audible.
Differences can be down to how well the pads seal, their compliance, how they change the volume of the cavity between your ears and the driver, their absorption or reflectivity for sound at varying frequencies, their shape (and how/what/where it reflects or absorbs) and how they sit on your head.
And those differences can be down to shape, material, design (e.g. vents vs. none), and even their age - since they tend to compress more with usage which changes the volume and shape of the air cavity.
The above FR plot shows the Elear with different pads in use (since all the Focal pads fit all their models). The output level of the source was not changed between pad-swaps, so you can see exactly what frequencies are elevated or attenuated with the different pad options.
And this is just an example where the pad dimensions/shape are consistent.