No you don't have to purchase same model . specially if you Buy from OEM like Dell you will pay a lot more. Best Buy or NewEgg are the best options.  you will need to get 2933MHz or Higher  If you get a 3200 mhz it will downclock to 2933 mhz to match the lower clocked module's frequency 
Im totally useless when it comes to pc parts. I just play with it. I bought the dell G5 last year and Im looking to upgrade the ram.  it has 16GB, 1x16GB, DDR4, 2933MHz listed currently. Could i grab a 3200mhz speed from like a best buy to upgrade? Or would I need to get the same make and model for the second? Specs that I could find: Ram: 16GB, 1x16GB, DDR4, 2933MHz  Motherboard: 0M6C7G      Version: A00      ??? I think thats all thats relevant. but cpu: 10th Gen Intel® Core? i7-10700F processor(8-Core, 16M Cache, 2.9GHz to 4.8GHz) gpu: NVIDIA(R) GeForce(R) RTX(TM) 2060 6GB GDDR6
Looking to upgrade my ram. G5