类别/子类别项的标签或嵌套集

Tags

create table product (id, name,...)
create table tag (id, name, description)
create table product_tag (product_id, tag_id)

NESTED SETS ?

Requirement Probably will hit 200 000 rows of products. 300-500 Tags(Category & Sub Category)

Question Is Tag good enough? A product would most probably have 5 Tags? Or do i really have to use Nested Sets

How about an array of tags? Modern databases support array of characters like char[].
And you can easily query this array for great performance.