Xbox and steam cross progression and microtransactions sharing

Hey,
So I've bought 30$ EA on xbox and linked my xbox account to steam. I'm thinking about buying another 30$ EA key but this time for steam. Now here are my two big questions:
1. Can i play with my character from xbox on steam (they are linked)
2. How do microtransactions work ? Let's say i buy myself some stash tabs on xbox. Will that stash tabs be available on my linked steam account once i get EA key for it ? What is the difference between buying stash tabs directly on ggg site vs buying them inside xbox client ?