Disable the Windows Defender will decrease the cpu useage at older devices up to 85% so it is possible to use windows 10 also on older devices
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender]
“DisableAntiSpyware”=dword:00000001
create a new file “disable_defender.reg” and copy / past the quote inside
after execution it should be disabled