Well it always depends on the writer. If what they say about Wakanda is true his tech should be better than Tony's. He might not be as high as Tony on the intellect list but "nowhere close" seems to be a bit of hyperbole. Isn't stark like 4 and T'challa 7? So if his resources are advanced already his tech and gadgets should be past Stark I'd imagine.
What is said can't contradict what's on the page. The Wakandans think they're hot **** because their whole nation is filled with all the technological marvels that NYC for example doesn't have. But that's more of a narrative problem, since NYC has to be "the world outside of your window" and Wakanda has to be some mystical futuristic country. Regardless of that, the best of Wakanda doesn't hold a candle against the best of the US. Even their precious "cure for cancer" which they're not sharing doesn't mean much because Norman Osborn discovered it himself (then turned it into a weapon 'cause he's a crazy SOB).
As for the Stark/BP thing, Tony is leagues above him, because he has the feats to support it. It's on page that he's "fractionally less smarter than Reed", whereas BP is somewhere on the 8th-9th spot, considering Cho is canonically the 7th smartest person, which was stated before Pym came back, which bumped him to 8, meaning that Panther should realistically be 9th.
Either way, power scalling aside, BP just doesn't have enough good showings. Not in the tech department, not in the physics department, not in the chess department. Not even in the bussiness department. Tony turned his arms company into a global juggernaut, and has also done it 2 other times, beginning from scratch as well. The only area where BP outclasses him are the Martial Arts.
Panther has beaten Iron Man and also out-witted him in non-combat situations.
The one time in the Priest run where he used Kleenex on a stealth suit (which was an Alt-IM) and that time during CW where Panther was on a diplomatic mission and caused a ruckus during his visit. Tony was holding back, and T'Challa came prepared. Then there's that time he beat the Avengers in his early appearances, but that's pretty much it.
But all those fights happened in BP books, which were objectively biased. Tony's suits are so advanced that it shouldn't even be a contest. Picosecond reaction time, full-blown invisibillity, grid connection, etc, etc. And that's only the basic stuff. If we move on to more "unique" suits, it gets even crazier. Not to mention the recent shape changing armor.
Realistically Tony could just nuke Wakanda and be done with it. And I'm not even joking. The man has developed a "Clean Nuke". He even rebuilt Asgard post Siege. And that's justthe tip of the iceberg.
He can summon the dead, which I don't know if past BP's were able to I thought that was just something T'challa achieved. I could be wrong there. He found a way to bring Shuri back to the living world so that's impressive as an intelligence feat.
The "control of the dead" thing was a one-time power that was a result of the Panther God literally granting him the abillity (which took about 4 years to have a pay off). It's nothing he worked for. It's a magic amp by Hickman. As for Shuri, she came back all by herself after going on a spiritual journey. T'Challa's machine just kept her in stasis.
Cap considers BP an equal in combat skill and strategy.
Sure, it doesn't mean he's smarter though. Tony has beaten Reed in chess while playing in 6 boards at the same time. The rest can be summed up in "prep", and there are countless of them. He also has tons of "thinking on his feet" feats, like the Time-Travel one, or how he kept evading Osborn & HAMMER while losing his intelligence. Or when he went undercover to search for the Sons of Yinsen. He's not just an engineer.
And even as afar as H2H, Tony has displayed skills. He's taken on Skrulls in nothing but his birthday suit, he's gone H2H with Mandarin, and he's received training from Cap, Widow & Shang-Chi. He's not as good as T'Challa, but he's no slouch.
But Stark in the comics is a damned beast. As is Doom. But from what I read, BP was always part of that league. That's why he is part of the Illuminati--the greatest heroic minds. If anything, this movie might actually bring consistency to Wakanda because the tech from the country that BP has seems to be all over.
T'Challa's good, but he's not athreat for the Top 5 guys. Doom is the only guy who's invented a Time-Machine, and the only people who can use it are him, Reed and Tony (back in the Camelot arc he and Doom build a new time-machine using parts of their armors). Tony has such a mastery of tech that he created a self-replicating city. Literally a city that kept growing and developing houses, appliances, etc, etc all by its own. Not to mention all of his suits.
Wakandan tech is average by comic-book standards. Hologram-Beads, a suit that absorves kinetic energy, flying cars. Nothing out of the ordinary.
TL;DR: T'Challa is one of the most dangerous humans in comics, but Tony has a recorded history of feats, and gradually grows more powerful. You know how Flash's whole thing is "Speed Force"? That's Iron Man and tech. Doom & Reed may be able to open portals to Hell and join Multi-Dimensional Councils, but Tony will nuke you before you can utter a word.