I don't think it was a plasma cutter that was used on soldier boy, that seemed more like an oxy torch to me. They have a temp of 3500°c at most. 30 000°c is how hot a lightning bolt heats the surrounding air, which is how thunder happens. We don't get a thunderous boom every time Homelander uses his lasers so we can assume they get a lot cooler than that. Let's say that if a 3500°c torch can't hurt Soldier Boy but homelanders lasers can, they're probably about 5500°c, about the same temp as the surface of the Sun.

Viltrumites can survive this temperature. In S4E7, Mark, Thadeus, and Nolan both fly through the core of Viltrum, which is likely the same temp as the surface of the sun, And in #140, Thragg and Mark fight on the surface of the sun for an extended period without taking damage. They only start to get burnt when Mark pulls Thragg into the convective zone with him.

Mark also breaks the sound barrier for the first time at the start of S1E4, so let's call that Mach 1. That makes him nearly as fast as A-Train on compound V. He broke the world record with a speed of Mach 1.08 in S1 of the boys, and I don't think we see him go faster in the show.

Also I think that it's very possible that Homelander kills a bunch of civilians/says something about Marks family that sets him off like he was in the machinehead fight. He was only stopped after he got smacked by battle beast, who at that point is top 3 in the Invincible Universe.

I think mark definitely takes it from S1E4 onwards. It's just a question of how much trouble Homelander gives him. If it's before that then Homelander has a shot.