PostgreSQL Objects design

Hi Listers,
I want to learn more about Table/Columns/Indexes  design.

   - How big the columns should be?
   - How many number of columns should a table have at max?
   - How many rows a tables should have at max
   - What are size limitations of different data types


Any books, blogs , videos, courses that you recommend I go over?

I have been an Oracle DBA , but only from a support and tuning standpoint.
I have never done this kind of work before, even in Oracle. So interested
in learning in this area?

Any approach that will speed up my learning?

-- 
Cheers,
Kunwar