Help with PVE 2 Cluster planning setup

We are migrating one of our online servers (OVH) from 1.9 to 2.2 release via a new server setup. The host node has 1 main OpenVZ container plus 2 other for logging and minor tasks.
For additional security we are considering hosting a second cheaper server that is capable of running PVE and that we would mainly use to backup our main servers containers as well as either mysql dumps several times a day or maybe include a dedicated container as a MySQL slave of some of the most important DBs. No NAS or shared network filesystem.

Our doubt is weather is worth setting up both as a PVE cluster considering that live migration won't be available and that in OVH we need some network tweaking for the cluster to work. I understand there are some obvious benefits as it will allow us to automate the machine dumps from one system to the other, see resources, etc but I am uncertain if:

• in case main system fails do I need any "adjust" on the backup cluster to access it directly and turn on containers. Would I restore the container from a dump backup just I would on a separate install.
• can I have other containers running on the backup system that are not available on the main one (assuming no ID conflicts obviously)
• is the process and network traffic overhead worth vs the alternative of two separate install and rsync syncros of DBs and containers every X hours.

Thanks.