Ramos, the Yashica lens seems to be plenty sharp based on the images you posted. However, I don't like the bokeh as displayed on No. 3 that much; it is a bit busy for my taste.
The advantage of using Leica M-mount lenses is the adapter is fairly thin; thinner than the adapter for DSLR lenses. But in practical terms, it doesn't mean much, at least to me. Down to about 35mm Leica M-lenses are generally fine on the Sony A7/r/s but wider than that it becomes tricky. Personally, I like DSLR lenses over the Leica M lenses in the 135mm focal length. The exception is the Leica 135mm f/3.8 Apo-Telyt but the price of the lens is steep and it is not that fast. If you like that 135mm focal length, I would look into lenses from Olympus OM, Contax, Canon FD, among others. Enjoy your A7s further!