A7iii -- separating exposure and focus

[modbuilder]

I want to use AF-S with Wide for focus on my A7iii, and be able to touch an exposure point on the monitor without that exposure selection affecting focus location.  I have studied the Sony instruction manual  about what setting does what, and searched the internet, but there are so many if/then qualifiers that I don't know how to set this up with confidence that I'm getting what I want.   On a tripod, I'm trying to shoot an ambient HDR-5 in jpg exposed to dark selection on the monitor, then switch to RAW with flash in TTL exposed to bright areas of the monitor.

I've got it set up so that shooting in jpg gives me the HDR-5 with one shutter press,  then switching to RAW let's me catch the flash single shot with another shutter push.  I think I've got the monitor touches selecting the different exposure spots between the 2 shots, but I can't tell if the focus remains Wide or follows the exposure touches.   I'm suspicious that both focus and exposure are following touches on the monitor because my focus seems softer doing this compared to just shooting wither a straight flash or ambient AF-S Wide shot without all the fussing around. 

I'm hoping to steer discussion to just A7iii settings to achieve the task without getting into why or which lenses, or comparing photos,  etc.    Apologies if this is not a specific enough description.  Thanks for your patience.  Looking forward to comments/suggestions. 

Thanks....... Bob R.