OK, so progress.
As for the issues with fields, you are typically far better to have extra fields than to have extra tables and have different tables for Companies in different Company Types.
One solution is to use form rules and open up sections of the form based on the company type. You will need to put the common fields at the top of the form in a common section, and then have a section open up for say the Cat specific fields based on a form rule that says
When Company Type is Cat,
Show Section Cat
Not that data entry fields many not be on form twice, so that is why you need to contrive the field layout to have the common fields like name and address and phone in a common section.
