Using a Unicable II LNB with an FBC tuner is highly recommended if you want to get the full functionality out of the tuner.

These days there aren't any 4 tuner boxes, so FBC is the only option for 4+ tuners. So you are looking at GB quad 4k or GB UE 4k, or Vu+.

There are only very few 4k broadcasts, but there are many other sources of 4k material, e.g. IPTV.

All FBC boxes are also 4k.