No, it is up to you and the page layout. You can test this to make sure the fields aren't spilling over. In the Form editor, you can control the length by character, but this has nothing to do with the # of chars a lead can put in there. That's up to the Field Management.
It's always good to figure out:
- what you want to know about your audience,
- how to capture it,
- and then report on it later.
Your initial question is the "How" but it's related to 2 other things as well. Here's some reflective questions to get ya started...
Field type: Will the majority of their responses fall into categories we can specify for them? (if so, it's more ideal for your reporting & easier for them to respond)
Question length: Keep it short & concise
Answer length: equal to field limits in Marketo AND any other synced platforms (like a CRM)