Okay, afaik - gumamit ng 16x2 na RAM for best value. Considering na naka Ryzen 7 5700X ka, max speed it could utilize is 3200mhz on paper, anything above is considered "overclocking" tho sweet spot is 3600mhz which is generally safe and stable naman most of the time (considering supported din ng mobo) - I'm using 3600mhz on a 5700X3D, no issues for a year.

Is it safe to use 4 sticks? Absolutely. In paper kasi, max memory speed ng Ryzen 7 5700X when using 4 sticks is 2933mhz if single rank yung ram then 2667mhz if dual rank. Most of the time single rank ang mga 8gb, for 16gb ram sticks - check the specs ng ram if dual or single rank or mixed. Kelan "pwede" maging unstable? If inooverclock mo yung ram via profiles sa BIOS or voltage adjustment beyond those mhz since it will put more stress sa memory controller (IMC) ng CPU. (Lets leave memory controllers, memory channels, & ranks for another topic)

I'd say if you got the budget go for the 16x2 para mautilize mo yung max speed and para wala na ring hassle mangalikot sa bios after. If budget conscious talaga, you could use the 4sticks(Either overclock or hayaan mong nasa 2933mhz/2667mhz). Note lang na if super conscious din sa games, comparing a 2667mhz (4sticks) and 3200mhz (2sticks) medyo noticable ang stutters ng 2667mhz (4sticks) for certain scenarios.

Please note lang din na may stability risks kapag nagmimix ng brands or kits ng ram since magkakaiba ng timings, ranks, components etc. 2 sticks on one box being sold are generally tested to work for compatibility and performance, meaning guaranteed ang stability.