A: it’s suitable for every game type ,every graphic type, the only limit is your skills
“My concern is performance. If final game has so many blocks, or large world, how it will be at performance?”
A: that depends on what you’re targeting for development generally speaking UE4 is focused on the heavy specs it was created with high-end graphics in mind if you’re targeting mobile devices i would not give you false hope unity is by far better for mobile don’t bother with unreal unless you’re targeting specific set of high-end phones and you want a graphically impressive mobile game that will suffer in performance anyway .
about pc and consoles UE4 shines in here , superior graphics and superior performance compared to the great graphics you get but as i said it was intended to work on higher specs so yeah good looking graphics come with price with UE4 the performance is decent but you will probably sacrifice many customers who own Intel hd graphics while with unity i have yet to see a unity game that won’t work on newer intel hd GPUs so that tells everything about what you should choose
Unreal is defiantly better looking and more complete out of the box without plugins but will work on less machines that means less buyers .