Postgres and Oracle differences and questions

I have recently been working on several projects that use MSAccess as a
front end to both a Postgres and Oracle DB. Unfortunately, I have
noticed some differences and limitations in Oracle that seem to make
Postgres look like a better choice for the application. My problem is
with the block sizing differences in PG and Oracle. It seems that when
mapping memo types from Access to Postgres you could create a text type
in Postgres that emulates the Access memo type, and you could define a
table with any number of these types of fields. In Oracle you can only
have one memo field mapped to a table with a max size equal I believe to
the block size, and if you use the max block size then you cannot define
any other fields in the same table.

I am curious how Postgres handles text types, is a var char or does it
allocate the full 8K for the text type. In Oracle, the size of the table
definition has to be within the block boundary, is the same restriction
true in Postgres.

D. Johnson
Spectra Data Systems Inc