How to stop 'b' keyboard shortcuts from scrolling through all the tools

You can also go to Edit > Keyboard Shortcuts > Tools and remove the shortcut letter from the Pencil and other brush tools.  You can see in this screen shot that I have also removed the shortcut from the Sharpen Tool.

For tools that you never use, remove them via Edit Toolbar and check Disable shortcuts from hidden toolbart extras

The thing to remember with this approach is that you can save Custom Toolbars, Shortcuts and Menus in Custom Workspaces'  This is a hugely useful feature as it lets us use a streamlined workflow for most of the time, and switch back to something like Essentuals for those times that we need the defaults.

I switch workspaces with a single key press using Function keys to trigger short Actions. The default Function key shortcuts are probably only useful for people with limited screen sizes, and single key shortcuts are far too valuable to waste.

I think F1 is the Function key you can't reassign.

Go to Preferences > Tools and see if "Use Shift Key for Tool Switch" is checked.