Need advice for a 'tag' table design
I would go for option 1 (two tables).

If you only plan to have 1000 content items (and in 3 years, not now), I don't think you will have many performance problems unless each content item is tagged with a dozen tags where most are unique to that item. And even then I don't think you'll see much of a performance problems. It also simplifies your structure if you have 1 tag table for every content type and then you decide to add/remove/change content types later. 

If you're really not sure, do you have the time/resources to build two sample DBs, one based on each structure, populate them with what you think is a realistic load (you can write a script/program to generate &amp; insert test data, right? with "boring" tags and content such as "content_1..content_2000 and tag_1... tag_5000) and actually test which performs better?