1000W PSU is the ideal for this combo, and enough for future upgrade. For example Corsair RM1000e or RM1000x.
The 27" LG UltraGear 27GP950 is an excellent gaming monitor that supports 4K @ 120Hz with HDR and 10-bit color for Xbox Series X, lacking only Dolby V...
@Matthew0000 RM1000x is a very good PSU overall, I have it for several years, never has any problem.