We have an official impeachment inquiry which doesn't feel much different than the investigations already ongoing.
What is different is that the Mueller investigation was all about what Trump did as a candidate and the obstruction he then did as president. There were several layers and it was complicated.
This inquiry is about a more simple situation and it all occurred with Trump as president. In fact in happened after the Mueller report came out.
This starts a new clock.
The inquiry could last a year before an impeachment vote is cast. Or there may be no vote.
But it is the House's version of an open trial.
They will ask Trump to testify. If he declines, it doesn't look good for him and if he testifies he will perjure himself about something.
Or it could happen quickly. That depends on what comes out and if Republicans get on board.
I can see Pelosi dragging this out and leaving Trump twisting.
As far as Trump releasing the transcript of the call:
Please. It's either going to have sharpie marks all over it or it will be the release of a benign call with any important discussions being withheld. We're not stupid enough to accept whatever he turns over.