I worked on a similar topic some years ago.
At the time I found very valuable the data from this website: https://baymard.com/
I was working on a B2C platform and the goal was to re-design the main navigation trying to organise more than 200 categories.
We have run 4 A/B tests, with two IAs. The first one, as you said, based on landing pages and the second one with a jumbo menu with all the main categories.
Guess at the end what was the recurring result for all the 4 tests?
Good luck with your research