I think I can understand your confusion. Here is a way of seeing the 2 seemings “different” results.
Usually, you would study or learn Young's Double slits experiment first and your teacher would derive some maths equations and you will be shown a picture with dark and bright fringes that are of uniform intensity. This is illustrated in the picture posted in post #3 (the purple curve which the legend states interference).
You can think of this as the “ideal” result which is derived by considering the “interference pattern from two ideal light sources” instead of from 2 slits of certain width.
After this, you would encounter the diffraction pattern from a single slit of certain width. This diffraction pattern result is again shown in the picture posted in post #3 (the blue curve which the legend states diffraction). After learning the diffraction pattern from a single slit, then you can deal with the interference pattern from the Young Double slits experiment because the 2 slits are of certain width NOT really 2-point sources of light.
In the Young Double slits experiment, we need to consider diffraction patterns (the blue curve) due to the individual slits and the interference patterns (the purple curve) due to the waves coming from the 2 slits, these combined patterns are shown in the bold red curve in the picture posted in post #3.
These combined patterns are also shown in the first picture in post #1.
Hope this “explanation” makes sense to you.