I will try to help you by going back to when I first set up my system to correct that horrible sound coming from my tv speakers. That was in 2013 and I had no technical knowledge at the time. I didn’t have a Panasonic tv, I had a Sony and am in the US. I bought a Pioneer AVR and researched for 3 front speakers to connect to it, left right and center. I followed instructions to connect speakers to AVR and then ran an HDMI cable from the HDMI ARC port on the AVR to the same on the TV. In the initial setup on both the tv and AVR, I turned on HDMI CEC. To watch tv, I changed the input to whichever HDMI ARC port I had plugged the AVR into.
If the tv is a smart tv that you have connected to the internet, you can select your APP, like Netflix, Amazon Video, etc that way. If your tv is not a smart tv, get a device that is, like a Roku, Blu-ray Player, Appletv, connect this device to the internet, connect it to an HDMI input on your AVR. You can then turn your tv on, your AVR on, your device connected to the internet and select the APP you want to watch, Netflix, etc. My setup works by using the tv remote to turn everything on (because I set everything to turn “HDMI CEC On”) when I power up the tv but I do have to then switch to using the AVR remote to select my internet device to switch input to my internet device. You could get one of those universal remotes and program it to be able to use one remote for everything but I haven’t.
As far as 4K goes, just get the AVR that has 4K passthru so you will be ready when you get a 4K tv but without a 4K tv, you won’t have 4K capabilities on anything. I hope all this info helps.