Click Try it first (changes nothing). The wizard goes through every access row and makes every decision a real import would, without writing anything, and without creating anything in Paddle. It reports:

Fix what you can (a missing price, a customer with two accounts) and try again until the report is what you expect.

Only access is imported, not payments. Every access row is imported with its dates and a state, whatever its payment state, which only tells a paid renewal waiting for its start from access that was switched off; only the access to products that Rows to import leaves out, and to prices you leave out, is skipped.

If the report shows dates that are wrong, or nothing imported, click Change where the data is read from on the previous step and check the columns and date formats, then try again.

Accounts keep their old password when Joomla can still check it (passwords Joomla itself stored, and the common bcrypt, Argon2 and phpass formats). Accounts counted under Accounts whose password must be reset get a random password instead; those customers use Forgot your password? to set a new one.