Do checklists and attachments come across?
No. Card fields only, and the import reports that in its warnings rather than leaving you to discover it. Plenty of teams keep the real substance of a card in its checklist, so this is worth knowing before you move several boards. If a checklist is genuinely the data, it usually wants to become its own table of rows linked back to the card.
Why do I need both a key and a token?
Trello splits them: the key identifies the application and the token authorises your account. Both come from your own Trello developer page and both go in. The commonest mistake is probably pasting the token into the key field, which connects without complaint and then fails on the first read, so it looks rather like a problem with the board than a swapped pair of values.
What happens to my lists?
They become the options of a Select field, in the order they sit on the board. That is the mapping that makes a Trello import feel immediately right: you can group by List and get the same columns you were already looking at, except that now you can also filter, total and report across several boards at once, which the board itself will never do.
Does the table keep up with the board?
It can. Importing the board again updates its table, matched on each card's Trello ID, so a card moved to another list changes list here and new cards are added; Keep in sync does that hourly or daily. Nothing is written back to Trello. A card archived on the board stops updating but stays in the table, which is worth knowing before you count it. Most teams settle on Trello for the daily card-moving and RowFold for the questions that span boards.
Does this work right now, or does it need approval?
Right now. Trello is one of the connectors where you supply your own credentials rather than relying on an application we registered with the vendor, so there is nothing to wait for and nothing that can be pending at our end. Paste the key and token and the board list appears.