Based on this information, I'll say that invasion Netero is stronger than Pitou by a decent margin.

Disagree with this. I think Netero would destroy the Royal Guards in a 1-on-1 (though Pouf's clones might make him difficult to attack. Idk how Netero would counter that, but I think he would somehow) but Netero <<< the Royal Guards in raw aura. Youpi was stated to have 10× the aura of Morel minimum, so he may have even more than that. Netero would only win because his Hatsu and his skill with it is ridiculously op, none of the Royal Guards are as talented as Meruem so they wouldn't be able to identify a pattern or bias in Netero's movements to get past his Hands. Even if they did identify a pattern, they're not as fast as Meruem so they'd still most likely fail to get to Netero. And their durability is also nowhere near Meruem's as shown by Gon, who's equal or at the very least close to Meruem, winding Pitou with 1 kick and near-killing her in 2 blows. This means that they won't have anywhere near as much time as Meruem to casually think about Netero's actions mid-fight.