I'm another end user dealing with this problem and sadly for once more i confirm what i have said to AMD in my mails.. "people shout and they keep their ears covered with wax"! In simple words, customers are trying to support them and they ignore us in return through their quickie work and unfixed problems. Unacceptable, releasing half-finished software (like they did with ccc to radeon software), and keep it in beta form even if labelled stable.
The only way I've gotten ReLive to work is via enabling desktop recording and starting the recording from there. Ive long since disabled the xbox dvr on windows 10 since that was a necessity to get the STEAM overlay to work. Then I uninstalled all the XBOX related apps from my system and subsequently went into services.msc and disabled all remaining xbox related services except for the devices service necessary to use my xbox controller in game. Instant replay doesn't seem to work when alt tabbing out of a game, at least it doesn't do so directly from the desktop. No tool bar appears in game at all when using the hotkeys as tested under DS 2 and Assassins Creed Syndicate, though both will record and stream to youtube with virtually no impact on system performance. I made sure that steam overlay and Uplay overlay options were both disabled while testing. As to whether the ReLive overlay and hotkey system works once STEAM and Uplay are totally uninstalled - I simply have no answer for you there as my games rely on having them installed. One quirk I noticed with ACS is that in order to get recording/streaming to work via ReLive - I had to switch from "fullscreen" to "borderless windowed" mode. FRAPS being on or off didn't make a difference to ReLive behavior.
hope this info helps