>>3016628>mirrorless>flat images You've been memed friend. Mirrorless actually allows for much more variety in lens design due to not being restricted by the mirror box, this means that you can use things like leica and zeiss rangefinder lenses, known for their "3d pop".
As a rule of thumb, the less lens elements, the less flat the image will feel, this can be seen, imo, most clearly with the latest sigma lenses, sharp as fuck but super flat.
What I'd recommend you do is look up some examples of the sony 55mm f1.8, and its awesome rendering, it's also insanely sharp in the centre from wide open and the edges sharpen up great stopping down. It also has a transmission value of 1.8, most 50mm f1.4 dslr lenses transmission value drops to f1.7, so in real use this lens is no slower than any other premium normal lens, despite its slower design. Pic related, dat pop.
Look how fuji measure up against sony/zeiss, kinda hilarious, fuji are supposed to be all about "the feel" of photos and they get rekt.
http://admiringlight.com/blog/sony-zeiss-fe-35mm-f1-4-vs-fuji-xf-23mm-f1-4/You could also use adapted lenses from any mount to give you the feel you want, if you don't think sony/zeiss have nailed it.
I'd only recommend the a7sii if you're shooting 70%+ video, otherwise you can save money and get sharper images from the a7ii or even sharper images from the a7rii, for stills the a7ii and a7rii outperform the a7sii in every way, including low light.
