For about 3 days until someone finds a way to break it.
It is the client you need to secure to prevent cheats like aimbots and esp/wallhacks (assuming you aren't sending too much data about events the player can't see/hear*) and the server authoritative to prevent things like RPM and physics/collision hacks. I guarantee it won't hold up long sadly once cheat devs get their teeth into it. Any attempt to discern cheating via "netcode" and/or game stats such as FairFight will either have to be done with a light touch, which will still let a lot of cheaters through, or it will have too high a false positive rate and ban too many legit players.
* For instance if a player is running behind a wall with positioned footstep sounds that can still be used to infer their position even if the netcode wasn't sending the actual player position.
Without getting bogged down in the details, I think a different way to understand Riot's approach here, is to consider the history of Riot and League of Legends.
A number of years back, League was being ruined by cheaters, Riot knows that cheaters can decimate the player base of a game - you only have to look at games like PUBG to see what can happen there. Yet, Riot managed to get League to a point where cheating isn't really a serious problem anymore, or certainly not what it was - it's also the worlds biggest competitive game, and it's free - so Riot knows how to do this at scale, long term and keep doing it.
With Valorant, that knowledge and experience has been there from the ground up. You can guarantee - if/when someone does figure out a way around the anti-cheat systems, Riot will throw untold amounts of resources at that problem and leave no stone unturned until it gets solved, because they understand the ramifications of not fixing it - especially with a free-to-play title.
I understand the scepticism though - in the end we'll have to wait and see how it holds up to the 'wild' so to speak
I've been waiting for a game like this to come along for some time now, as CS:GO MM is very stale and I don't want to pay for features that, given how much cash Valve rakes in through skins etc., should really be in the base game. With all the talk from the various streamers I've dropped in on so far I'm getting low-key hyped.
Yeah, we were playing with a whole load of influencers and streamers, at the event we laid on for them over the weekend, and the reactions we got were so great - to be on a server playing with some of the big name streamers was amazing, although playing against some of the actual pro CS players was... lol