How to show Forms in nodes stored in the node tables
What do you mean "generate form on the fly"? As in: the form for page "page/form" doesn't exist in a canonical state but is generated based on variables such as date/url/taxonomy? Or is it just the default values for the form etc? 

In anyway: the options to have a form on a page are:


Hardcode HTML into the node content, e.g. &lt;form&gt;&lt;input&gt; etc
Use hook_menu to create the page and use the form API 
Use hook_menu to create the page and use the straight HTML
Use hook_nodeapi to add a form to the content with the Form API
Use hook_nodeapi to add a form to the content using HTML
Use a module such as webforms to add the forms


I would suggest either 2 or 4. When you say that hook_menu generates these plages "on teh fly": that's not true. hook_menu is only run on cache clear, and assuming you're using caching then the generation of forms isn't going to make much difference to your server. This may be a case where you're sweating about optimisation unnecessarily. 

Using Form API gives you a load of tools that you'd otherwise have to handle yourself - validation, submission, sanitising, standardising, etc.