Just be aware that those tutorials are four years old. Depending on which generations of devices you’re targeting, 2014-era mobile devices are MUCH more capable than they were back in 2010, with many devices featuring multiple cores, 64-bit CPUs, much more capable GPUs, and high-PPI screens.
Honestly, I’ve been surprised what we can get running with UE4 on mobile devices without doing a lot of special work to make things “mobile ready”. We haven’t gotten to the point where we’re optimizing, and we see great frame rates. Early on, we were focused on keeping the poly count low and now we’re facing a situation where we have to re-model a bunch of our assets at higher poly counts so they look good on modern mobile devices.
Mobile can’t handle the poly counts that the XBox One and PS4 can handle, but current generation devices are capable of handling pretty complex scenes and UE4 does a good job of creating shaders from your materials that run well within the limitations of mobile hardware (at least on iOS - we haven’t done a lot of Android testing yet).
Our general rule of thumb with models and textures is now to shoot for the moon - create high poly models and larger texture maps than we likely need, then create game assets by resizing textures down and retopo’ing models to lower vertex counts. There are great tools available for lowering poly count, and resizing textures downward is rarely an issue, but going the other way almost always involves quite a bit of rework.
Also, when you start from high-poly models and large texture maps, you’ll have assets you can use a few years from now for the next-gen redux version, or that you can re-use in your next game.