A Solar System Is a Big Planet, but Is It Possible?

Is this constraining the size of a habitable zone for an extra solar planetary system, like narrowing the size of it to wearyou ot those pressure gradients? Or is it just that it also depends on the chemistry of the planets, the size the magneto sphere, et cetera. What would be habitable to mars sized planets might be different than what's habitable to earth or venus size planets. And and then wea get down to the life as we know it versus life that's living beneath a shell of ice.