Is it because this site has monstrous volume? Can I subscribe — perhaps via RSS? — to topics I have knowledge in? Is there any tool that helps with filtering questions?
Is it because this site has monstrous volume?
Can I subscribe — perhaps via RSS?
Yep! See this link.
Is there any tool that helps with filtering questions?
We have the search box up there on your upper right. Here are some search tips, if you're interested.
As @cogwheel suggested, you can highlight or dim questions on the front page based on your interests with customizable Interesting Tags and Ignored Tags on the right sidebar.
We also have the 'Tags' tab. Click it to see a list of popular subjects, and from there you can see questions with that tag. (Or you can click a tag anywhere else to see similar questions).
Is it because this site have monstrous volume
That's certainly a huge part of it
Is there any tool to help filtering questions?
You can set up "interesting" or "ignored" tags that will highlight questions depending on your preference. And since your interesting tags show up in a list, you can easily browse the newest questions for the topics you're interested in.
can i subscribe (rss?) to topics i have knowledge in?
You can view or subscribe via RSS to specific tags, or just refresh the front page to your hearts content. The site offers many great ways of filtering content (you can even run your own queries on their database, plus there is an API on the way).
Having more users than population of eastern Iceland does help to get good, quick answers out there.