disable (gray out) share button:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Word\DisabledCmdBarItemsList]
"TCID1"="26594"
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Excel\DisabledCmdBarItemsList]
"TCID1"="26594"
[HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Powerpoint\DisabledCmdBarItemsList]
"TCID1"="26594"
(do same for any other office apps you have)
remove login button:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Common\SignIn]
"SignInOptions"=dword:00000003