Permissions of widget files

Hello,

i moved wordpress from cpanel hosting to linux vps.

And there is an issue with permissions. Example on previous 644 worked, but on new linux must be 666

so example, template files dont wanted to save from wordpress admin.

Now there is a bigger issue with Widgets.

Widgets i have in my wordpress widget section are NOT loaded in sidebar.

I want to ask where are located these files and what is proper permission of them?

or if you ahve other permission tips, have similar experience moving WP to linux server

thank you