Question about creating a DNS load balance between domain controllers

I'll get the easy part out of the way first:

Here's my question though, how does it work? is it round robin? who answers first? the dc the computer is connected to or the DNS the computer is connected to?

Yes, it's round-robin by default.  You can disable round-robin in the properties pages of the DNS servers (under the Advanced tab, I believe), but there's typically no reason to do this.  So the first time a DNS server is queried for that name, it'll return the IP address of the first corresponding host record.  The second time it's queried, it'll return the second one, etc.  It should be mentioned that you won't see this exact behavior on a client.  Multiple queries for the same name from a single client will return the same IP address for a while, because the client will have that address in its resolver cache and won't actually query a DNS server until the cached record expires or the entire cache is flushed.

i know i could use the default domain name instead, but it had connections to other servers except for the domain controllers.

Are you saying you've got blank host records in DNS (host records with the name "same as parent folder") referring to machines other than domain controllers?  If so, that's a problem.  Those records are used by domain members to locate a DC, and they shouldn't ever refer to anything but DCs.

To answer the question, there's no true load-balancing mechanism built into DNS.  Round-robin DNS does load balancing only on the most basic level; it doesn't care whether a given server is down and will return its IP address anyway.  Network Load Balancing (NLB) is outage-aware, but I can't think of a way to make it work in this scenario.  If those apps that you're running are AD-aware, they should be able to use AD's built-in mechanisms to locate a DC that's running.  Have you actually experienced problems with them?