In 2 Corinthians 12:1-4 it sounds like Paul is talking about someone who had an out of body experience. But according to James 2:26. If you ever have an out of body experience you would have to die first. Because it says in James 2:26 the body without the spirit is dead.
At verse one I find the word ' vision ' is used, so it would be a ' vision' as also found at Matthew 17:9 was a 'vision'.
The 'third' heaven he saw is the ' third ' heavens of 2 Peter 3:13.
Please notice there are three (3) heavens and three (3) earth's mentioned at 2 Peter 3:5; 2 Peter 3:7; 2 Peter 3:13.
The ' first ' heaven of verse 5 was the "OLD" corrupted heavens of Noah's day.
The ' second ' heaven is the "NOW" heavens since Noah's day to our day, meaning those governing over mankind.
The ' third ' heavens is the "NEW" coming heavens and earth meaning a righteous governing heavens by Christ, and a righteous new earth or earthy society of people starting at the time of Revelation 7:14 when those of Matthew 25:31-33,37,40 are counted as being ' righteous ' ones.
So, Paul was Not disagreeing with James because living Paul saw this coming future paradisical time in vision form.