What info from other cosmere books do I need to know before Rhythm of War?

So my cousin has been trying to get me to read SA for years and I finally started with WoK a couple months ago and just finished oathbringer a few days ago. Currently a 1/5th of the way through Rhythm when I got a call from him berating me that I hadn’t read the mistborn series before starting RoW.

Because I’m a relatively slow and impatient reader, I don’t really want to break from finishing the book I already started with WaT loaded up on my bookshelf…I’d rather not read the mistborn series before continuing lol.

I don’t mind spoilers of the mistborn series, so could someone fill me in on critical information I should know from those series that connects into the storm light archives? Specifically relevant to RoW? To avoid future SA spoilers for myself, I’m currently at the part where: Adolin, Shallan, and her lightweavers are about to go to shadesmar to seek council with the honorspren / find restares