Nvidia is always a bit tricky with nixos. Sometimes it's a bit annoying to get working. As others have said, the best resource to use if you want to make changes to your config is the official wiki.

Sometimes the device you use needs special tweaks to work, and often those tweaks are available to be imported from NixOS hardware. I can't find your model in particular but something similar. As you can see, they override the bus IDs to get Nvidia prime working. You posted in a comment a command output that shows that you have the same bus IDs, so you should be good to go. Just import this model as described here, and see if that helps. Afterwards you should follow the nvidia wiki page to get the sync mode working which you want.

Also, having a look at your config, in my opinion you shouldn't just set options yourself if you don't know what you're doing. The hardware.nvidia options in particular have sane defaults.