you wish it were that easy didn't you!
there's a 1-5 week leadtime. guy orders from distributor he doesn't keep stock.
The FreeSync version (XR341CK) yes, it is only up to 75 Hz. The X34 G-Sync version instead is up to 100 Hz, if the monitor cannot reach it you can get it exchanged. Acer also confirmed this is the case to OcUK (and TFTCentral too I believe?).