We always go for open access publications! For the majority of the journals we submit to, the Open Access fees are covered by government agreements with the publishers no extra costs for us!
At this stage a .pdf document of your work is not sufficient anymore, and the Editorial Manager (EM) needs to build the .pdf based on your latex files.
I had proplems with the citations of my work written in Overleaf, when building the pdf in the EM. The final output displayed instead of the citation numbers. It took me a long time to figure it out:
Then it should work hopefully.
Useful:
https://service.elsevier.com/app/answers/detail/a_id/36917/supporthub/publishing/kw/latex/