I’ve just installed and upgraded Suite to the latest version (7.1.2) and have edited the config file to point to a Sugar database (Sugar and the database was running the latest version 6.5.17) - I’ve not had any problems so far…
I’m assuming this is a reasonable/recommended way to go to transfer to Suite?
There is an upgrade package here which allows you to migrate from SugarCRM CE 6.5.x to SuiteCRM 7.1.2.
That is the recommended way to upgrade. You can point the instance at the db, but you will need to run a Quick Repair & Rebuild in Admin -> Repair and execute the changes(bottom of the page) as there will be none of the additional tables in the SugarCRM database that are in the SuiteCRM database.
Generally it is dependant on your setup. Sometimes it is your user, sometimes apache, sometimes www-data. It can differ from server to server. This may be something your host can confirm if you run into problems.