https://www.gamerevolution.com/guides/655124-horizon-zero-dawn-pc-lag-fix-how-to-stop-lagging
 
Horizon Zero Dawn PC might be the definitive version, but the jump from console to PC hardware can also bring new problems. Some players are having a sub-optimal experience thanks to a Horizon Zero Dawn PC lagging issue. If you fall into that group, stick with us for the Horizon Zero Dawn PC lag fix that should smooth out your performance.
 
In order to implement a Horizon Zero Dawn PC lag fix, you’ll need to take several troubleshooting steps to figure out what exactly is causing the issue. From the obvious to more obscure solutions, everything you should do is laid out below.

HORIZON ZERO DAWN PC LAGGING FIX

Horizon Zero Dawn PC Lag Fix | Close intensive background applications

1. Press Ctrl+Alt+Del, then click the “Task Manager” option.
2. Click any unecessary apps (everything but Steam and Horizon in most cases), then click the “End task” button.

Horizon Zero Dawn PC Lag Fix | Run the game in fullscreen mode
Running Horizon Zero Dawn PC fullscreen, instead of windowed, can lower your chances of getting stuttering lag spikes. You can change to fullscreen in the “Settings” menu.
 
Horizon Zero Dawn PC Lag Fix | Update your Nvidia or AMD drivers
Having out-of-date drivers can casue major performance issues, so naturally you’ll want the latest versions.
How to download Nvidia divers

1. Visit Nvidia’s “Download Drivers” page.
2. Input the details of your Nvidia component(s) to check for and download the latest drivers.

How to download AMD divers

1. Visit the AMD website.
2. Input the details of your AMD component(s) to check for and download the latest drivers.

Horizon Zero Dawn PC Lag Fix | Adjust your graphics settings
HZD PC spends around 15-20 minutes on initial boot analyzing your system to decide on the ideal preset. Due to this process we recommend trying the other fixes first, but if you still get lag, you can manually tweak the visual settings.

1. Navigate to the “Settings” menu in-game.
2. Reduce all graphics settings to the lowest.
3. Increase one option and return to gameplay.
4. Keep doing this until you can identify which setting is causing lag.
5. Once you’ve identified the issue, revert your other settings back while keeping the culprit reduced or off completely.

I hope this helps with the lagging issues

sounds like a train wreck ... not the best "solution" but maybe a stopgap while the "bug" is getting fixed by publisher ... lets hope so

There is No lag all the jack wagons just love to whine 
and i got a weak ass intel E5 2620 v3  with a 2080ti the  game runs just fine

aka_STEVE_b
I hear it's great fun to play - but I can wait awhile until everything gets patched properly.
Plus it will be on sale by then , so it's a win-win 

Yes it is very fun to play. I played it on the PS4 and beat it 5 times.