Apple pays a lot of attention to the user experience when using a Mac computer, they have been in the forefront of that industry since the beginning. Having to use PC peripherals with macOS can be quite frustrating, specially when you are used to the smooth experience that Mac peripherals provide.
These are some of the apps that help me keep the macOS experience as close to using Apple peripherals as possible.
Karabiner-Elements
brew cask install karabiner-elements

PC/Windows keyboards are plug-and-play in macOS, but certain keys are mapped contraintuitively (Alt/Option, Win/CMD), or not mapped at all (media keys, volume, brightness, etc). While modifier keys can be set up through the macOS keyboard preferences, this utility helps you get all keys mapped to match the functionality of an Apple keyboard.

MonitorControl
brew cask install monitorcontrol
Control the brightness, contrast and sound volume of your external displays from your keyboard (applies to both PC and Mac keyboards). Your display must support DDC commands (most modern flat screens do).
Mos
brew cask install mos
Smooth scrolling with any mouse wheel.
sensible-side-buttons
brew cask install sensiblesidebuttons
Navigate back and forth almost any window with a history (Safari, Finder, etc.) with your mouse side buttons.
Magnet

Windows has a great feature, callend Snap, that allows you to snap windows into specific places of your screen. This makes it super simple to take full advantage of your display real state, and align your windows in a layout that fits your workflow. Magnet allows you to do that, and more, in macOS, both dragging windows around, or what's more interesting, through keyboard shortcuts. Not sponsored.
Do you have any other apps you think are essential? Let me know in the comments!