200+ rep on other sites will give you the 100 rep bonus which is enough to do the regular things like comment and up-vote.
As for tagging, I would argue that tags are not strictly transferable and what makes a good tag on one site will not always make a good tag on another site. To that end I think its good that users need to spend some time on a site before being able to add new tags there.
So how much rep should you earn on a site to understand what makes a good tag? 49 (150 - 101) seems like a fairly small amount to me.
If there is a tag you want to use but does not yet exist, you can request it in your question or in a comment attached to the question and, if it's a reasonable tag, I'm sure someone will add it for you.