Have been currently using the free browser extension in Chrome, and am looking at subscribing to the full programme.
If I start to use the full programme is it best to keep the browser extension or un-install that and use the programme only?
The extensions have been developed to detect the presence of the full program. You can then use the extension to block ads for the full program (the rules created in the extensions automatically are added to the main program) or you can use the Adguard Assistant in the full program to block ads. Really, it's all your choice if you want to continue using the extension or not.