question about ram

[Blissfulterror]

im want to upgrade my memory but not sure if i should just buy the exact same kit to add to the two open ram slots or buy a higher speed 16gb ram kit and replace the two that are in there 
or can i mix the ram i have with a higher speed 16g ram kit? the info for the ram i have is bellow.
 
 Motherboard:
      CPU Type                                          HexaCore Intel Core i5-10400F, 4000 MHz (40 x 100)
      Motherboard Name                                  MSI Z490-A Pro (MS-7C75)
      Motherboard Chipset                               Intel Comet Point Z490, Intel Comet Lake-S
      System Memory                                     16304 MB  (DDR4 SDRAM)
      DIMM2: Team Group TEAMGROUP-UD4-2400              8 GB DDR4-2400 DDR4 SDRAM  (18-16-16-39 @ 1200 MHz)  (16-16-16-39 @ 1200 MHz)  (15-15-15-37 @ 1126 MHz)  (14-14-14-34 @ 1051 MHz)  (13-13-13-32 @ 975 MHz)  (12-12-12-29 @ 900 MHz)  (11-11-11-27 @ 825 MHz)
      DIMM4: Team Group TEAMGROUP-UD4-2400              8 GB DDR4-2400 DDR4 SDRAM  (18-16-16-39 @ 1200 MHz)  (16-16-16-39 @ 1200 MHz)  (15-15-15-37 @ 1126 MHz)  (14-14-14-34 @ 1051 MHz)  (13-13-13-32 @ 975 MHz)  (12-12-12-29 @ 900 MHz)  (11-11-11-27 @ 825 MHz)
      BIOS Type                                         AMI (01/30/2021)
      Communication Port                                Communications Port (COM1)
      Communication Port                                Standard Serial over Bluetooth link (COM5)
      Communication Port                                Standard Serial over Bluetooth link (COM6)

[Guest]

Probably get the same kit. Use Cpu-Z SPD tab to get the part number of the kit you have. 

[Blissfulterror]

thanks