An ideal (minimal) 2.1 setup

What amp/processor?  Or, are you just using the digital out from the tv?  Also, with only 2 channel it will make a difference regarding speaker placement.  You need the speakers tighter to the screen for movies but probably pulled out into the room for music?  just my concerns.
The sound on OLEDs is better than most tv's but still crummy.

If the program content has center channel info, and you have no center channel, then don't you have to downmix to forced 2 channel mode?

If you just don't hook a center channel up, the center channel signal is still NOT in the front L and front R.

I guess the movies are more casual than anything serious (not looking for theater loudness). More priority to music to I would place the speakers apart for music and not have a center as I'm trying to keep it as clean as possible. For the KEFs it would be out from TV since its an active. 

How about a NAD M10, some Revel M106s and a T/7x?  With eARC the audio will be automatically downmixed to 2 channel…no loss of information, and the speakers will give a solid central image without a dedicated channel. Dirac Live will tune the system response to your room below 500Hz. If you don’t love the M106s substitute another similar speaker. 

The size of the woofer matters a lot.  I've never found little bookshelf speakers satisfying for rock.  Little speakers + subs can have the same frequency response as large floorstanders, and can be comparable on some types of music, but nothing large scale.  If you listen to Beethoven or any full-bodied rock I think you'll be disappointed with little bookshelf speakers despite plenty of deep bass from a sub.