I had a fairly thorough look on the Greg Archives for this (https://greg.thegreatarchives.com/) and I've found some relevant info, although not conclusive answers.
1) I think this opens up some interesting questions about the mechanics of telepathy and psionics in the world of Bionicle. When asked if Krana and infected masks can control beings like Agori and Glatorian, Greg said no. When asked if the Mask of Mind Control could be used to control them, he said no, "because it works on AI, which Glatorian do not have". However, Orde was able to use his psionics powers to read Gelu's mind. That suggests that whatever psionics is in the Bionicle universe, it is common to both the living beings of Spherus Magna and the MU.
EDIT Additionally, he says here that Kanohi would generally work on Glatorian, when the person asking specifically mentioned the Rode (Mask of Truth) here: https://greg.thegreatarchives.com/2008-2010/page250#post9986 so I guess the Rode works based on Psionics too?
I think whether or not Rahi Control would effect Spherus Magnan insects depends specifically on whether it works by trying to interface with AI, or if it uses the more nebulous "psionics" in some form or another. Personally, I would bet on it not working on Spherus Magnan creatures, but that's just me.
2) Greg said that "Rahi control cannot be used on insectoids, and vice versa". I think the use of the word "insectoid" could suggest that it doesn't have to apply to the strict IRL definitions of "insect" (not that it could even technically apply since Rahi and Spherus Magnan animals are not the same as real-world animals. So I don't think it the power is limited to true insects/hexapods. Just things that generally fit the insect/bug/creepy-crawly category.
I've noticed Greg usually finds that kind of adherence to real-world terms restrictive and tries to avoid being to shackled by them. Based on the other related answers, I would theorise it has more to do with the complexity of the creature the Makuta is trying to control. A rat-like Rahi is mentally significantly more complex than an ant-like Rahi, and that probably has to do with why Rahi/insect control are different categories (although there's more to it, as he's explained elsewhere).
Regarding Makuta at least, I bet their telepathy is psionics-based, so whilst I don't think their Insect Control powers would work on Spherus Magnan insects, they could probably use their telepathy to at least influence them, if not outright control them.
Hope this helps, even if it doesn't definitively answer things.