Joe, your initial message states "...without me having to map or manage or enter many settings - just the one that changes which synth is in use (or close to it)." Thus it appears to me that you are looking for a General MIDI sound source. This would eliminate Kontakt, SampleTank and all of the other best sounding sound sources. Note the best sounding comes from the more expensive, sometimes specialized, sound sources.

What genre of music are you going to play with this sound source? Some GMs have better sounding strings than others, some better horns, or ensembles, or guitars etc. The only GM that allows you to change sounds, AFAIK, are the old soundfonts(sf2). With a free sf2 player and a free sf2 editor you can pick the best patch for you and place it in the GM sound source. But these will only sound as good as some entry level sounds like those that come with BiaB/RB.

Thus my advice to you and anyone else that wants to really get into MIDI is to quit using GM, learn about setting up non-GM MIDI sounds and learn about MIDI controls, i.e CCs. More work, yes. More cost, yes. But one hell of a lot better sounds. DL the free Kontakt player and listen to a few super MIDI tracks through it and you should see what I mean.

http://www.native-instruments.com/en/products/komplete/samplers/kontakt-5-player/free-download/

I want my last spoken words to be "I hid a million dollars under the........................"

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware