Please recommend me a G-sync, 2560x1440 or 2560x1080, 144hz monitor for under 500 euros. If my pc specs are important I'm running RTX2070 super, I5-8600k, 16gb.
I would go with a FreeSync monitor instead for the following reasons:
Nvidia 10-series and later cards support GSync, for the most part*.
Lower price: GSync is basically the "Nvidia tax" as it requires a separate module, which monitor makers have to pay Nvidia for. An otherwise identical monitor with FreeSync is notably less costly than the equivalent GSync monitor.
* if you want to be absolutely 100% certain on this, while lots of FreeSync monitors not on this list work just fine, you can go to this page, and filter the "Type" column (first column in the chart) on "G-SYNC Compatible"
I would go with a FreeSync monitor instead for the following reasons:
Nvidia 10-series and later cards support GSync, for the most part*.
Lower price: GSync is basically the "Nvidia tax" as it requires a separate module, which monitor makers have to pay Nvidia for. An otherwise identical monitor with FreeSync is notably less costly than the equivalent GSync monitor.
* if you want to be absolutely 100% certain on this, while lots of FreeSync monitors not on this list work just fine, you can go to this page, and filter the "Type" column (first column in the chart) on "G-SYNC Compatible"