You asked
7artisans af 18mm f 2 vs sigma 19mm f 2 8 dn art?
The 7Artisans AF 18mm f/2 is the one I'd pick if you shoot Sony. It's brighter, at f/2 against f/2.8, so you get more light and more background blur. On APS-C it frames like 27mm on full frame, and it fits Sony E bodies only.
The Sigma 19mm f/2.8 DN Art frames almost the same, like 28mm full frame on APS-C. It's the better choice if you might move to Micro Four Thirds, since it also fits that mount. It's light and cheap, but it's a slower lens, so in dim rooms it will need a higher ISO.
Both are non-stabilised, autofocus, APS-C primes. For a Sony APS-C body such as the a6400, I'd go with the 7Artisans 18mm f/2.
Written by Claude from this site's pages.