PGA definitely adds throat hit, and it seems to me that it enhances the throat hit of nicotine in eLiquid, although that is a subjective assessment. Also if you put say 25% PGA in your mix, it thins the glycerine so that it goes in the cart faster/easier, and stretches the eLiquid (makes it last longer). Around here, at least (midwest USA) PGA is about the least expensive component of DIY eLiquid, so it seems it adds a little savings as well by using it as an ingredient while adding benefit. You could thin with distilled water less expensively, but I don't think it adds anything and thins the flavor of the mix.
Note that for some flavorings, the alcohol in the flavorings is sufficient and additional PGA doesn't need to be added. I like to add 3 ml Lorann's Creme de Menthe to a 7 ml PG/VG mix, and the Lorann's is virtually all alcohol in this case, so I don't add any additional PGA, it would just weaken the flavor to do so.
There's no practical physical way you could get an alcohol "buzz" even if you were vaping straight PGA with an eCig. google personal alcohol vaporizers. If you want the effects of one ounce of alcohol, you have to breath in an ounce of alcohol. And that would take so long you could never build up enough alcohol in your system to get a noticeable "buzz".