The difference between Universal Web Adapter and a Web Adapter is when any web application is interrogated using UWA only one main parent frame will be created but for WA for every sub-children in the web application, a separate parent will be created which can be noticed by interrogating same web application with both adapters and verifying in Object Explorer. Besides, all the interrogated controls are always associated with the Adapter. As UWA supports only Chrome and Firefox to change to IE or Edge as we should go to different adapter types all the controls should be reinterrogated. In addition to that when the controls are re-interrogated the automations that are dependent on the old controls also should be updated with the new ones.
@SoKaps The latest versions of the UWA (after 19.1.70) include support for Edge and Chrome. It is just a flag on the adapter, so you can use the same adapter and controls to work with that application is either Edge or Chrome without re-interrogating anything or changing your automations. The Web Adapter as mentioned below is for IE only and cannot be switched to a different browser, so re-interrogation within the UWA is required in that case.
@SoKaps Possibly. You should test thoroughly if you make a change like that. I would not expect any differences though since both Edge and Chrome use Chromium to render pages.