Mhh, insects in general IIRC are also constrained by the fact they have exoskeletons: i.e. their internal organs are just in a bag. So they can’t grow too much or they just squish I think.
Imagine them being able to become vertebrates. You can have insects the size of cats I think before the osmosis breathing tubes they currently have are not a thing. Lungs would be the next thing I guess.
Disclaimer: I’m not a biologist and just make stuff up from what I remember from high school biology, and it was last millennium!
Oh right, I’ve read about that on coconut crabs I think. There you go, they are already half there.