Agent commission and making an offer

[Sam M.]

How does agent commission work now?  Haven't bought a property in awhile.

If I submit an offer, does the offer include the commission or not?  

If the seller is on a 2.5% with their agent and I'm at a 3% with my agent as a buyer, would the seller's agent ask for 3%?  Or vice versa.  

The commission can vary by agent.  I don't see the commission posted as it used to be on Redfin/Zillow.  (Am I missing something?)

What is the standard?  3% per agent, is 2.5% doable? 

Edit: For SFH