First, I found your pencil lines a charming addition of detail.
But this is how you learn about opacity in various brands. Mungyo Gallery Soft have, by and large, excellent opacity and blend well together. You might consider a small set. They're a decent size, though not square.
Also, I find blending OPs is easier with tools, from regular paper tortillons to silicone-tipped clay shapers. You'll have better control staying within your desired areas.
A little trick to sharpening an OP stick is just to keep scrap paper nearby and use it to rub an end of an OP to get it flattened, which gives you a nice edge. Softer OPs only need a few swipes.
Also, depending on the brand, the thing I like about OPs is that, after a few layers have been added, they become much easier to move around and blend. One thin layer on textured paper can be difficult to manage. Once they're built up, though, you can use the clay shapers to push them around, and get some nice texture in there.