Beyond that I didn't really have much of a clue on what the movie was about, and an early review I read said you should expect to be confused for at least the first hour, before the plot starts to fit together in a way you'll understand.
To give you the basic outline I'm just going to give you the IMDB version because I don't really know how to expand on that in any meaningful way:
Armed with only one word, Tenet, and fighting for the survival of the entire world, a Protagonist journeys through a twilight world of international espionage on a mission that will unfold in something beyond real time.
At two and a half hours I was concerned this film might drag a little because Chris does like his exposition. Fortunately that wasn't the case. There are scenes with quite a bit of exposition but, because the ideas of the film are a little complex, the exposition scenes are helpful in trying to sort out the action.
Despite that, I don't really know what I just watched in terms of the story? I don't feel I really connected with any of the characters or that any of them had that much of a story arc. Overall it seems like I watched a very complex magic trick, and then spent the second half of the movie watching how the trick was done behind the scenes.
That, in itself, was very engaging, and more than enough to hold my attention.
John David Washington, as the lead character (only known as The Protagonist) is great. I haven't seen his other work but he's very credible here as super confident, suit wearing, action hero type (he could be a contender for the first black James Bond after this performance).
Robert Pattinson's, Neil, is possibly the most likeable character of the leads, who kind of hints that he actually enjoys the job he's been hired to do simply by giving a slight smile here and there.
Elizabeth Debicki initially seems under used as Kat, in a way that made me wonder why she'd even want the role but fortunately she gets much more to do as things unfold.
Kenneth Branagh is like the standout performance as Andrei Sator, though this is the first time I've really seen him play an unlikeable villain type character. He really sells it though. I like Kenneth Branagh, but I didn't like his character here, at all (in the way you're supposed to not like him).
In reading about how the film was made, it is hard to believe so much of the action is practical effects and not green screen. Keep that in the back of your mind as you watch.
Overall I did enjoy Tenet but it is definitely a movie that needs a second viewing. I kind of got the gist of it but I'm sure there's plenty I missed. Don't feel bad if you end up feeling confused on the first viewing too. From what I've read, even the cast were rereading their scripts multiple times trying to wrap their heads around it all.
It is definitely an interesting idea in time travel movies that could make for some interesting stories if Chris wanted to explore his world further. See it on a big screen if you can.