Hey Emanoel and CBR+PNK peeps!

In the Runner File....under the Skills section...the line about Expertises states: 

EXPERTISES don’t add + to a roll, but allow you to trade+ for an EDGE—and vice-versa—when they are applicable.

So I have two questions.

1) EXPERTISES don’t add + to a roll, but allow you to trade+ for an EDGE. 

I take this as if you have +2 in Coding and an Expertise in that for Hacking....then when it comes to an Action Roll using the Coding skill to hack....the player can choose to have the +2 from the Coding skill....or take +1 for Coding and get an EDGE on the roll (then the Edge would be translated to either Decreased Threat or Increased Effect based on what fit the narrative) . Is that correct? 

2)"and vice-versa-when they are applicable." 

Does this mean a player could trade their EDGE in a narrative moment to add+ to the roll?  So lower/remove an Edge and have one extra die added to the roll?

Ex. In a scene where the PCs have established superior position and created an strategic advantage for an ambush of a target....they would have an EDGE which mechanically could translate to having +Effect for a Action Roll due to it being an increase to their effectiveness in that moment.....but if a player wanted to increase the likelihood of a success...they could forgo the EDGE (+Effect from the tactical position) granted by the fiction and instead have an extra die for the Action Roll?  Which leads them to having a higher chance of success. Is this correct and or an reading into "vice-versa" incorrectly? 

Thanks in advance for your help!