Craft Commerce 2 — Remove Line Item (and other actions) Knowing that all other actions besides update-cart has been deprecated I'm curious what needs to be passed with the action to remove a line item from the cart using a button as opposed to check a checkbox &gt; update cart (essentially removing a click for the user). 
The same would apply for +/- buttons/inputs for adding/removing from quantity.

I see in the example templates there's a checkbox input with name="lineItems[{{ item.id }}][remove]". Is it as simple as changing the input to a submit (or button submit) using the same name tag contents? Would this then also carry over to be posted via ajax in the same way as an update-cart action?

That's a long question. Trying to wrap my head around the changes as I'm just getting into Craft 3 and Commerce 2...
Is it as simple as changing the input to a submit (or button submit)
  using the same name tag contents?


Yes.


  Would this then also carry over to be posted via ajax in the same way
  as an update-cart action?


Yes.

Everything can be done on a single line item basis to the update-cart acton, just use the new param names.