Is this bundle worth it for a budget workstation?

Yes if you need many cores cheaply for office work, VMs or a home server. Expect to add more memory and accept an older platform with limited BIOS support.

How much memory should I add?

Plan on at least 16GB, and 32GB or more for VMs. The bundled 4GB is only enough to boot and test.

Does it support DDR3 and DDR4?

The board lists both DDR3 and DDR4 DIMM support, but not mixed in one build. Check the exact module type and speed the BIOS accepts before buying.

Can I use multiple graphics cards?

No. The board does not support multiple GPUs and is not aimed at mining. Use one card for display or light gaming.

What storage does it take?

It has SATA III ports for SSDs and hard drives. There is no U.2 or modern high-speed slot, so NVMe needs an adapter.

Is the CPU included and installed?

The Xeon E5-2673 V3 is included, but you mount it yourself in the LGA 2011 socket. Check the pins and apply thermal paste before installing the cooler.