For an Xbox or PS4 you don't need the highest end. Ssd: 1tb https://www.amazon.com/dp/B07D998212/ref=cm_sw_r_cp_apa_i_hglWCb4JE43CJ SSD
Case: https://www.amazon.com/dp/B00OJ3UJ2S/ref=cm_sw_r_cp_apa_i_JklWCbPKETZGN
I have 3 of these cases, I use a 480gb SSD on my oneX and I have a 240gb SSD for my wife's oneS.
An SSD would likely help you more. I'd recommend a 1 TB like this: https://www.amazon.com/SanDisk-SSD-PLUS-Internal-SDSSDA-1T00-G26/dp/B07D998212/ref=sr_1_6?keywords=ssd&qid=1648269500&refinements=p_n_feature_three_browse-bin%3A14027460011%7C6797521011&rnid=6797515011&s=pc&sr=1-6
Extra RAM may help in certain games, but it is unlikely to make much of a difference for COD. If you want to have serious gains, you're going to need a new motherboard, RAM, and CPU at the very least.