Question Need advice for laptop ram upgrade.

Dec 24, 2018
I have an hp pavilion x360 14-dh0047tu (Maintenance and Service Guide).
It came with Samsung M471A5244CB0-CTD memory module (4GB DDR4-2666Mhz, CL 19), but the laptop has a limit of 2400Mhz.

The laptops guide only states DDR4-2400 dual channel support and so does the processor (i3 8145u).

I'm planning to add another 4gb of ram and am looking at various options like Crucial, Kingston and the exact same Samsung module as well.
Since the laptop is gonna down clock to 2400 is it worth buying the same module (2666) or can i go with the cheaper alternative like a 2400Mhz CL17 Crucial module and risk a bit of non-compatibility?

Also I have a SK Hynix HMA451S6AFR8N-TF module (4gb DDR4-2133MHZ, CL 15) lying around, would it work with the Samsung module or will it be not be compatible at all as the processor doesn't support it?