Questions related to the calibration of a VNA?
What calibration you "need" depends very much on how accurate you need your measurement to be and how bad are the internal errors in your VNA set.

What I learned to call SOLT (short/open/load/thru) calibration is certainly a good choice for 2-port calibration on many VNAs (historically this calibration was mainly used on "dual 6-port" VNAs, but I suspect VNA technology has advanced since I learned this stuff).

But if you have modest accuracy requirements, or if your VNA doesn't support a full 2-port calibration (some lower-cost models don't), you might get away with a simpler (less time-consuming) calibration using fewer measurements, perhaps only a thru response measurement.

Or if you are working in a transmission line technology like microstrip where it's not feasible to produce a very good Short or Open standard, you might want to use something like the TRL (Thru/Reflect/Line) calibration.