Question 3 is a bit of a spoiler, so I’ll skip answering that one right now, hope you can forgive me. 
All I can say is, the blurb I wrote about the game in the OP deserves a fair bit more scrutinity if you want to know about that…
As for the rest, though:
There are no hard limits, no. Technically speaking, the MC has a fair few, in the form of Super Strength, Flight, and Energy Manipulation. That’s not counting their Adaptive Evolution.
Same thing with Latooni, who has Telepathy, Telekinesis, and a very different sort of Energy Manipulation from the MC (this will be important later).
Forlorn also has three, and Ignis… um, spoiler, but you’ll see eventually why she’s the golden goose of her family.
The second part of your question goes more into this one, I think, so I’ll answer them together.
There aren’t any conceptual powers in the story, and it’s very unlikely that any will show up.
I agree that such powers are pretty OP and awesome to see, but they tend to be kind of hard to wrangle and limit properly (Lord knows how many mangas I’ve read get endlessly attacked for not using them properly), and some times, the story turns into figuring out how to sidestep them instead of the actual plotline.
I don’t really think I’m capable of wielding such esoteric skills properly, so the most you’re going to see regarding time and space is that someone can see the future (and even then it’s unreliable), and someone that knows precisely the correct way to move 100% of the time.
The big boy powers of the setting are going to be more common stuff. Atmokinesis, (forceful) power transferring, lifeforce manipulation, that kind of thing.
@Alfa_Rico Don’t worry, it’s not rude at all. 
As to your question, there is another being close to the Monarchs’ level (as close as can be, anyway), and they have met.
But in general, it is meant to be unfair.
The Hero-Monarchs aren’t figures which the cast is meant to eventually shoot past, or threats capable of being contained. They’re meant to be these unstoppable figures which can’t be stopped despite individual effort who have their own agendas, goals, and who you can’t force to see things from your point of view, because they hold all the cards.
Those two are the epitome of what individual strength can be, and they’re just… beyond. They both push the supposed masters of the world (be it the Western or any other) out of the limelight, with all the good and bad that implies, as well as all the decisions it will lead people to make.
After all, you didn’t think I made the destruction of an empire’s whole army when it got in their way their most famous act for absolutely no reason, did you?
The Hero-Monarchs aren’t meant to be balanced, because their point is that they break the scale.
Right now, their power matters not, because the Queen is dead, and the King remains chained (which is, perhaps, a better situation than the Queen being alive and still holding the chains). They aren’t the destabilizing, geopolitical shattering, ‘cause the world’s armies to desert en-masse’ force that they would be, because they don’t care enough to remind the world why their mere presence kept three empires paralyzed for a decade.
But if people keep poking, if the Cult keeps putting out bait, if the world powers keep taking it, if foolishness outpaces caution, and if the last, sole chain is broken before the beast-tamer’s return…
Well, in the words of Forlorn and his opponent at the end of Chapter 10:
"Heaven have room."
