At the moment it is not possible to know when one is close to reaching the table size limits. This makes it difficult to plan future developments and architect a system's development. The first we know is either when a solution fails to import or when it is not possible to add more columns to the table.

Further, there is no clear definition of how large each column is in a table, so making estimations on when the table limits are going to be reached is also not possible based on the columns already in the table.

My suggestion is that a "current row size" be calculated and exposed through the Power Platform Admin centre for each table in an environment.