baking a Souffle to make it as much liquidish as possible I have found this explanation for example:

Bake the soufflé: For maximum lift, it’s best to heat your soufflé
from the bottom up — in other words, the direct heat of your oven
should ideally be coming from below. Also, place the soufflé on the
bottom rack of your oven so it’s as close to the heating element as
possible. Alternatively, you can preheat a baking sheet in the oven
and place the soufflé on top of this to bake; the baking sheet acts
like a heat source.

But I can hardly agree with that. Is there a way to use only the top heating element in the oven so that the top will get crust and not burned and the bottom will get baked properly?
Maybe the solution is just to use narrow and taller cup?
I get your point.  A souffle is often just set, but sometimes, as in when making something like a chocolate lava cake, the cooking is completed early so that the inside remains liquid. I would not use the top element of your oven, as this simply over cook the surface.  I would just use the oven rack in the center, rather than placing the souffle on the bottom rack.  That has always worked fine for me.  This is a time sensitive product, and much depends on the size of the container you are baking in.  It is often best to bake these in single serving ramekins so that you have greater control over the timing. For a liquid center, keep a close eye on it.  Remove after it has risen and the top has set.