Hello aryasharmag4,
Welcome to Apple Support Communities. It sounds like keyboard clicks are enabled from Settings > Sounds & Haptics, but the volume is inconsistent within apps. Right?
Since this happens within different apps, it may be best to also check for sound settings within these apps. Some apps have separate volume controls.
For your notifications, check to see if 'Change with Buttons' is enabled from the same page above (Settings > Sounds & Haptics). This will change your alerts with your volume buttons and may help. You can also test with a different notification sound to see if this issue may be related to a specific tone. If needed, reference Change iPhone sounds and vibrations - Apple Support.
Take care.