FWIW Total Commander's EXE and DLLs are around 8MB (the installer is 4.2MB) and uses around 6MB of RAM right now (for comparison, the new UWP Calculator uses 18MB of RAM). It is not written in pure C/C++ nor uses Win32 directly but instead it is written in Object Pascal/Delphi or Free Pascal/Lazarus (depending on the version you use) and uses VCL or LCL (well, it probably does use some Win32 directly too). Also runs on any Windows PC from Win95 to Win10.
I mention this because Delphi and Lazarus are quite high level environments to work with with rich frameworks and libraries yet you can create very lightweight applications with them (the executables will be a bit fat compared to what you can do with pure C/C++ or even pure Free Pascal, especially with Lazarus, but resource consumption is still low).
You do not need to use C/C++ with pure Win32 API to create lightweight applications and even if you use those there are frameworks that allow for easier development (e.g. WTL, Win++ or libui to mention some).
I mention this because Delphi and Lazarus are quite high level environments to work with with rich frameworks and libraries yet you can create very lightweight applications with them (the executables will be a bit fat compared to what you can do with pure C/C++ or even pure Free Pascal, especially with Lazarus, but resource consumption is still low).
You do not need to use C/C++ with pure Win32 API to create lightweight applications and even if you use those there are frameworks that allow for easier development (e.g. WTL, Win++ or libui to mention some).