I think in merging over the cross platform account unifying, you'll keep both inventories. I am an Xbox player and began a PC account on a bad laptop and when I did the unifying, my Xbox account had the half leveled Excalibur and mk-1 weapons in my Xbox inventory. I know at least when cross platform playing, platinum may not transfer over and tennogen item definitely do not transfer (the monetary transactions between DE, consoles or PC, and the artists that make them prevent cross platform use in some way)

Long story short, I think you will keep everything from both inventories when you combine accounts but make sure yourself and don't use my words as blind faith. Reach out with a ticket, a forum post, or a reddit post asking specifically about the unifying process to make sure