Update. I figured out how to forget a remote on the Roku Ultra 2020. I didn't know it wasn't necessary.
I re-paired the Roku 4 remote to the Roku 4. The Roku 4 remote has the headphone jack but not the TV on and Volume like the TCL remote. Since I use the Roku Ultra with an AVR those buttons don't help me much. I'll talk to the wife about moving the Roku Ultra remote to the TCL. If I can't do that I'm thinking I might be better off with the TCL being plugged into the firestick so as not to confuse which Roku remote I should be using.
While watching the Roku 4 add the YouTube TV channel I was shocked by how long it took. That leads me to believe the old 720p TCL simply doesn't have the RAM necessary to run the bloated YouTube TV app. It seems to run Netflix and other channels without stuttering.
So last question, can I reprogram my TCL remote to work with my Roku Ultra? I have to assume so but it's worth asking. If I do, can I get the TCL remote to turn off my JVC TV?