With Smshosting inserting the lead magnet is very simple, because botim data during the form creation phase you can choose which response to send to the user and select an attached file (in case you want to give a PDF for example)
The Lead Magnet is not mandatory, in some cases it is fine, in others it is probably not necessary. Always think about your target user, put yourself in their shoes and try to understand if in their place you would leave the email .
Now this is a great way to test if your lead generation strategy is working.