We are seeing that when designing surveys on survey123 web designer, the designer starts to get significantly slower as the amount of questions keeps going up.
For example if I put 60 random questions in the designer at once, it already starts to feel sluggy.
Is it documented if there would be a maximum amount of questions that sould be on the designer in order of not to feel it slow at the time of designing and that Connect starts to be a recommendation?
I appreciate links that gets me to something documented or any comment about this issue.
I don't believe there is a theoretical limit for the web designer. It is designed for simpler, quick surveys. At 60 questions you will benefit from moving to Survey123 Connect and getting the full design experience. The performance hit may be the type of questions (lists) content (images) or something else more than the no. of questions.
You may encounter similar issues in Survey123 Connect as well. At some stage, calculations + lists will make the survey take more time to load. Publishing in connect, the survey will still load in the web browser. There's more discussion on this and how to avoid it e.g. theoretical limits on number of choices in lists before recommendation to move to external lists.
Treat Survey123 like app development. Build and test, then reduce and refine if the user experience or performance is not there. Keep guiding principals - can you load in pages? Reduce the complexity etc.
Re Connect vs Web, most of the time it's a question of functionality vs ease. Personally I lean towards Survey123 Connect most of the time except for simple and fast surveys. But I started off with Connect before the designer. Would recommend a similar approach for spatial professionals looking to heavily utilize Survey123. I'd consider a web survey to be pretty short - maybe 10-20 questions? But more considering my experience building the survey than performance :D.