will it affect the performance if i store about 1.5mb worth 100+ string_array data inside strings.xml?
Any other best method to store them?
I don't think there would be any noticeable performance problems with 1.5MB string.xml, except that your app would take up a little more RAM for the time it runs. It's fine, as long as it doesn't grow beyond, say 2-3 MBs, which might leave less RAM for other portions of your app.
Android will throttle the RAM anyway, so, if during your testing, you don't see any OutOfMemory errors, you are good to go.
But then, there might be other approaches, depending on what exactly your requirement is.