Where can I find a list of locations and dates for these tournaments? And what exactly are they, just an "Open" Tournament at like Pax or some other convention or what?

https://www.galacticqualifiers.com/

Next one is April 13-14 in the UK

https://billetto.co.uk/e/uk-galactic-qualifier-milton-keynes-2019-tickets-308606

Seems like if you buy a ticket to go you can register on the first day to play.

We will be taking registrations for each of the four GQ events separately as players may not be available for all of them. The entry price covers all GQ and non draft side events for the whole weekend

https://www.cascadegames.com

these website is also have GQ locations in U.S. and Canada