System tablespace should be more than 0 because we will dropping and creating so many objects. There will be lot of space defragmentation. So if pctincrease percentage greater than 1 system will coalese it automatically.
well by default itīs 50 anyway and there is not much point changing it afterwards since the segments are already created with that pct increase value, even you change at tablespace level the segments will still have pct increase 50
For the SYSTEM tablespace, you can specify EXTENT MANGEMENT LOCAL in the CREATE DATABASE command. If the SYSTEM tablespace is locally managed, other tablespaces in the database can be dictionary-managed but you must create all rollback segments in locally-managed tablespaces.