moving from MySQL to pgsql

Hi !
At present, I am using MySQL as backend for my work.
Because of the licensing implications, I am considering to shift from MySQL
to pgsql.
Typically, my apps are multi-user, web based or LAN based.

1) Read over the internet that ---
Postgres is not threaded, but every connection gets it's own process. The
OS will distribute the processes across the processors. Basically a single
connection will not be any faster with SMP, but multiple connections will
be.

MySQL is multi-threaded server so it can use many processors. A separate
thread is created for each connection.
source:
http://dcdbappl1.cern.ch:8080/dcdb/archive/ttraczyk/db_compare/db_compare.html#Comparison+of+Oracle%2C+MySQL+and+Postgres+DBMS

In what way it might affect my app performance?

2) I run MySQL from a USB stick.
There is no installation required (on WinXP.). (not tried on Ubuntu)
Is it the same for pgsql?

3) Can I simulate MySQL's TINYINT data-type (using maybe the custom data
type or something else)

Thanks,

Vineet