Hi.
Small is fine, no dimensions problem. Speeds are fine, power consumption in use is fine and temperature is low too. But I don't know what is the difference between connections in B and C version of adaptors. Why is used one pin in first and another in second adapter. I now that the some this pins in this area are used for power settings of SSDs (for example SSD_PWR_FET_EN).
Like is described here:
Upgrading 2013/2014 Macbook Pro SSD to M.2 NVMe
And yes, both work fine, except hibernation. I have a changes settings to disable hibernation. Actually I still test it, but I think that its OK now, battery power drops is about 3-5% per day. Its almost what declare Apple (30 days in sleep/hibernation mode). I chose ADATA for lower power consumption, price and availability in my region.
Now, I know that small Sintech adaptor version B is better and is in lower price. I bought both from Sintech and shipping was about 5-10 day.