The perfect game engine = going straight from art to code. An engine that takes art as input and outputs a whole complete game.
Many of the engines do almost that, but generally there is some level of coding or scripting involved.
Unity has everything you could possibly want to make any kind of game.
Construct outputs games that work well even on older computers.
Many people seem to like Godot.
Pico works well on older devices also.
But I don't think any of those tools are going to run well on a tablet.
It's generally best to learn some Javascript, using just Javascript and html you could make your own web games from scratch.
For me, when developing, I like to have a really big screen and a keyboard, if your tablet can have a keyboard,
you would be able to do Javascript development generally comfortably,
but I would say that it's best to have a desktop/laptop with as big of a screen as you can get, and a mouse and keyboard.