Further update - I really did not like the "cluttered" nature of the fireTV UI compared to the Roku UI. Additionally, I use my streaming device in conjunction with a Logitech Harmony Hub and Amazon Echo Dot and unlike the Roku's channels, the installed streaming apps on the fireTV are not "accessible" to the Harmony app as Favorites, or to the Echo Dot as Friendly names. This means you cannot use Alexa to directly start the fireTV activity AND run one of the installed streaming apps like you can with the Roku - e.g., saying, "Alexa, tell Harmony to turn on Netflix" results in an error (Alexa does not find a corresponding favorite or command) when used with the fireTV; whereas with the Roku, it results in the Echo Dot activating the corresponding Harmony activity to start the Roku and then automatically starting the Netflix channel.
So, to return to the Roku platform and regain these features, I ordered a certified refurbished Roku 3 from Amazon. It works perfectly with no audio/video lag, supports the 1080p video capabilities of my TV and plays DD+ audio. Good solution for me until the 4K upgrade, which I am really not that anxious to do at this point.