Don't do that, you can't. The config tarball is not only target and model specific, but may also contain device specific content (MAC addresses and more) - only use it as reference.
Only if you know what you're doing, extremely selectively and after careful review of each file - but probably the files you care about most will not be interchangeable.
two most important file is, to be honest, almost unusabe
/etc/config/network
/etc/config/wireles
in network file, there is too much difference between devices, and in recent OWRT there is swconfig -> DSA transition
so, no, only to open in notepad or whatever text editor and look at them what was old setup
wireless file, it is unusable again, only in form of "reminder", pure text
recent OWRT was changed wifi device names
and every type of device has its own hardware description
ex:
option path 'platform/10300000.wmac'
which will be totally different for different devices
so, no
you need to open these files in TXT editor, look for passwords, or other settings, but nothing else
You will spend more time and effort trying to recover dubious settings from older files than reconfiguring from scratch. So reconfigure from scratch. Only use you previous settings to copy important data such as MAC, IP, password, etc.