Okay, resolved ... - the game (engine) apparently doesn't like DX11 for some reason - CS said to deactivate DX11 via command line parameter : "-d3d11Enable 0" - nVidia driver crashing is resolved by deactivating the hardware accelaration in Chrome - yeah, seriously.
I had the same issues, Telekom in germany ... I started using a VPN Service with an exit node in the US (Private Internet Access for example) - this usually solves the lag issues