They are listed.
For Strength, it's size catergory. Every size up form Medium is double strength. Wth giants being the largest beings with humaniod proportions.
Ah good, I was worried, let me just crack open my Monster manual.... huh, weird. You just said that "Human, Inhuman, Superhuman, and Mythic" are listed as the size categories. But my book says "Tiny, Small, Medium, Large, Huge, Gargantuan" Was there an errata I missed?
For Toughness its HD.
For Speed, its speed.
Oh, okay I'll just.. hmmm, nope. I even did a CTRL+F for inhuman or superhuman in the PHB. No results anywhere near the mention of Hit Dice or Speed. Hit Dice seem to generally go from 1 to 20, but of course some monsters go up to things like 33 HD. Speed also seems to range from 5 ft to 150 ft. But they don't seem to be divided in any way.
So, how about this. Since you are clearly quoting rules for what these terms "Human, Inhuman, Superhuman, and Mythic" mean, and I just can't find them. Why don't you tell me the page numbers they are defined on? Then we can figure out why my books don't seem to carry these categories which are obviously part of the game and not something you just made up on your own.
So the question is can your warforged, human, or elf lift like a humaniod, an ogre, or a giant.
"But my PC can get the same strength as a true giant with epic boons and magic items"
Yes,but they still have to roll a check to throw a 1,000 lbs rock. A cloud giant does not.
Your elf still needs to be dragon orgin to have an effectively higher HD.
The question is whether a fighter should be able to lift 1000 lbs effortless and just throw the Wall of Force back in the wizard's face without a check?
And the answer is yes. Yes they should be able to lift 1,000 lbs, maybe not effortlessly but certainly reliably. And I'd prefer to just shatter the wall of force rather than try and make rules for a snow-plow blade of force.
Because, this isn't really a question. You are trying to make it a question by partitioning things and saying that martials can't exceed certain arbitrarily decided limits. Because they are human. And forgetting it seems that my entire point is that not all martials are human.