Concepts is described as 'The digital design sketchbook of the future. It’s powerful, flexible and smart, so you can go from quick sketches to beautiful and precise illustrations in a single app. Enhance your creative capabilities with our infinite canvas, flexible multi-touch shape guides' and is a digital painting tool in the photos & graphics category. There are more than 25 alternatives to Concepts for a variety of platforms, including iPad, Mac, iPhone, Windows and Android apps. The best Concepts alternative is Inkscape, which is both free and Open Source. Other great apps like Concepts are Krita, Microsoft OneNote, Affinity and Xournal++.
Tayasui Sketches doesn't offer enough technique and detail as Concepts. It focuses more on the simple aesthetic side of things; the layers prove to be a big problem as well since I cannot import images like on concepts.