Hi @Aris
I use lots of shortcuts in ZBrush. I did make the choice of overwriting some of the default ones since it’s much more useful to me to have them set to brushes rather than actions I seldom use.
Here’s my setup:
I set numbers from 2 to 6 and Alt+numbers from 2 to 6 as some of my most used brushes.
I left “1” as repeat last because it was the one number shortcut I found useful in my workflow.
Then I have Ctrl+1 and Ctrl+2 as my favourite mask brushes.
Ctrl+Shift+1 and Ctrl+Shift+2 as Selection brushes and Ctrl+Shift+3 as a slice brush.
Then “7” is left at default Frame Mesh (Frame Mesh Border With Curves)
As I’m on an AZERTY keyboard I also have a “<>” key next to the Left Shift.
I set Alt+< to ZModeler brush, Shift+< and Ctrl+Shift+< to two of my custom menus (that pop up at the cursor position if you call them with a shortcut).
I also set Ctrl+< as a shortcut for one of my plugins pie menu.
Then I have Ctrl+Shift+V set as Polygroups>Group by Normals
Ctrl+C as Crease
and Ctrl+Shift+C as Crease Polygroups
I changed the default symmetry shortcut X because I found it was way too easy to press X by mistake and screw up your model by sculpting in or out of symmetry not even knowing that is the case.
I set X to something harmless - see-through mode (slider).
Alt+X switches solo mode on and off.
Shift+X toggles Active Edit Opacity (Transp button in Transform menu)
while Alt+Shift+X toggles Ghost mode.
To turn symmetry on or off I need to go out of my way and press Ctrl+Alt+Shift+X 
I use Ctrl+Alt+T to show and hide the timeline (since I use it constantly to store camera views).
I have Ctrl+Shift+D set up as duplicate subtool
and Alt+Shift+D as duplicate subtool only leaving the current subdivision level and deleting higher and lower levels (it’s a macro)
I use Alt+Shift+S as export document.
Shift+L activates and deactivates Boolean Render mode.
Alt+W acts as Weld Points,
Alt+F as Fill Object (color) and Alt+Shift+F as Fill Object with Background Color (macro)
Alt+C is set for Go to Unmasked Mesh Center (Gizmo and Transpose Line)
phew! There 
Funny thing is that I use these all the time so I don’t think about them. Only one or two of these I use seldom enough that I forgot I set them (fill object with background color and one of the plugins’ pie menus)
There are no problems or conflicts with these - apart from overwriting default 1 through 6 shortcuts.
There is a small bug in all ZBrush versions that makes it a tad more difficult to switch to a sculpting brush straight form the transpose mode. It’s sometimes necessary to click the brush shortcut twice for the brush to switch). I’m used to it though and don’t notice it. It sometimes applies to choosing a brush from the brush palette by pressing B>Z>M etc. so it’s not really the shortcuts’ fault.
I’m just used to double tapping brush shortcuts.
hope this helps
cheers
Rafal