Tuple identifier (tid) - object identifiers

In Postgres documentation there is a reference of the tid that is by
default inserted for each tuple in the database where is it, which takes
an extra percent of the database's storage space.
It's referred that is of the general form:
tid : <block number, tuple index within each block>
Is it possible afterwards the installation of Postgres to not have
it on database's size. Or most important can we see its size (tid) per
tuple or totally to the whole database (size of the block number , size
of tuple index within each block)? Does it have some default values and
which are those?Thanks you

SWTHRHS TOYRTOYNHS
(tourtoun(at)csd(dot)uch(dot)gr)