HexWalk is much simpler than ImHex. It uses Qt so the GUI is more native (ImHex, of course, uses Dear ImGui). HexWalk is much more "fixed function" than ImHex. ImHex is basically a core hex editor view with a canvas you can fill with an endless stream of plugins.

For a comparative newbie, I'd say HexWalk is simpler than ImHex and offers a decent baseline feature set for simple tasks. I prefer the native UI widgets to Dear ImGui ones. It gains features each release and is slowly catching up to HxD (which is IMO the Gold Standard for "fixed function advanced features hex editor," to the point that I run it in Wine even on Linux and OSX). Some elements of the UI feel wasteful/clunky compared to HxD, but a lot about hex editors boils down to personal preference.