If an internal employee is filling out this Marketo form, will the website behaviour function on Marketo work for the lead, or will it simply track the employee's behaviour who filled out the form on behalf of the lead?
To use the exact Marketo terms: by default, the Munchkin web tracking session (i.e. cookie) will be (re)associated with the lead that filled out the form. The form has no way of knowing, on its own, that the person who filled out the form was doing it "on behalf of" somebody else.
If you want to ensure that the form fillout is taken in isolation and doesn't affect web tracking, you want the "referral form" pattern -- search the Community for lots of discussion of the pattern.