In order to create the exam sheets without solution, everything works fine with exams2nops (apart from the logo which is not taken for some reason). I can add the name of the institution, change the title, and setup a non-English language and the date. But if I want to create examsheets with the solutions, then, if I understand correctly, I cannot use anymore exams2nops, but I have to use exams2pdf with template="solution" which does not take into account the institution, the date, the language, nor the title.
Any help?
You are correct that exams2nops() does not provide a version of the PDF with the {solution} environment and the complete answer text. The nops_eval() only provides a HTML report with the correct boxes that needed to be checked.
So to produce a PDF as desired you can run exams2pdf(...) or exams2pdf(..., type = "solution") after setting the same random seed that you set before running exams2nops(). If you want to modify anything like layout/logo/language/etc. in exams2pdf() you have full flexibility but need to do the work yourself. That is you need to come up with a LaTeX template file that looks the way you want. As a starting point you can take solution.tex from the package. The easiest way to get all templates shipped with the package is to run exams_skeleton() and then look at the templates folder.
Background info: exams2nops() also just calls exams2pdf() internally after setting up a suitable LaTeX template file based on the arguments specified by the user.