Probably. Insectoids might be slower.
There are several issues though. When most people think "giant insects", they think of insects, only scaled up. Except, this is biologically and physically impossible. When you scale things up, the mass scales by the cube - you'll need very thick legs (think elephants) and most likely a standing posture. You'll also need a proper respiratory/cardiovascular system to transport all the extra oxygen required - not very insect-like if you ask me. Even the "giant insects" in the fossil record aren't so giant at all, they only have a large wingspan, and their body's cross-section is actually smaller than some of our giant beetles today.
But let's suppose we make those modifications and end up with something like a rhino with 6 legs. If we stopped here, then it would be about the same speed as a vertebrate of equivalent size. This is because the muscles involved are pretty much the same between insects and vertebrates, their strength is determined by their cross-section, which scales slower than mass. This is also one reason why bigger creatures are slower, relative to their body size. Insects are only fast (and strong) because they are small; there are plenty of fast, small non-insects like bats and lizards.
Now let's consider the protection. You mentioned "the same relative protection", but this quickly becomes impossible if you scale up too far. For physical reasons, materials become much weaker the bigger they are. Drop an ant from 100 times its height and it would walk away without a scratch. Do the same with a giant ant and it will crack like an egg. Our giant insect would need fancy materials for its exoskeleton to approach the same level of protection, maybe some form of metal (hey it's possible). But it still won't be of the same relative strength unless we start delving into cybernetics. And yes, the extra mass would make them even slower.
So to recap, for a realistic human-sized "insectoid", we'd have
- Same leg thickness
- Standing posture
- Same strength
- Slower speed (than vertebrates of similar size)
- Metallic exoskeleton
Doesn't sound like an insect to me. I suggest handwaving and/or magic.