There should be an option to set your own buttons for different functions. So for example, if you want A for the horn or whatever then you can have it.
I would love to have that as an option in the settings, y on xbox one is not assigned and I would like to assign to something like master key toggle/headlights.
Also you can do the low horn on controller you hold x then press left stick. Check the control schemes and look at the operations shift controls scheme. You can even do cruise control up and down and pub release and override while holding x. Also holding right stick and pressing left on the d pad you can cycle through the interior cameras. And holding Right stick and pressing right on the d pad you can cycle through the exterior cameras. Also in exterior cameras you can hold right stick and left stick up to zoom in and then press right stick to zoom back out. Also holding right stick and holding down on the d pad, you can upload a screenshot to dtg live. So remember to look at the different control schemes
On xbox certainly yes. On PS, don't known. It is described in the control scheme as, changing the operation. Me too. But Y, is assigned to lifting the butt from the driver's seat. Unless, as a switch.