To me low light photography isn't about street, bar, sport and events, but family pictures at home with f5.6-f8.
I am assuming you are talking candids and semi-candids (fast poses without careful set-up). Not sure why you need f5.6-f8 for indoor family pictures. I usually try to go more open and try to get away with no flash as long as possible. An on-camera flash adds substantial complexity to the mix - as you are always have to adjust to your changing circumstances.
I might pool out from the cabinet used to be famous GF lightsphere to smooth shadows

On-flash diffusers doesn't smooth shadows substantially. Bouncing your flash does.





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