Solved! Go to Solution.
If responsiveness of the web form is the main concern for you. You can add a Marketo form on this page and use CSS to make it responsive. See https://community.marketo.com/MarketoArticle?id=kA050000000KyqgCAC. Then Marketo actions would be a cinch.
In Salesforce - if you wish you can add a trigger on lead creation for salesforce only steps.