Hi guys, I'm a blackberry keyone user and I'm pretty much used to. Due it have only 3 gigs of ram I began to use Mini Desktop launcher, that goes only to 40 mb of consumption. My doubt is, there's another lightweight launcher outside the non distraction ones? (Olaunche, ulauncher, mlauncher...)
Have you looked at KISS? Extremely lightweight and customizable. You can go from the most minimalist approach with text only and selection of apps to show to crash things like visual effects and icons for every single installed app.
It's not user friendly at first and that's certainly why it doesn't get the love it deserved. But once you figure it out, you can build the launcher you want and never have to go back to the config anymore.
The web browser app should be defined at the system level by defining your default apps in Android. Search engines can be defined in the "search settings" of KISS.