Is a supertransporter considered a different aircraft type than the one it is derived from? By supertransporter I mean the SuperGuppy (derived from the Stratocruiser), the B747LCF dreamlifter, the A300-600ST, the airbus beluga XL, and any other aircraft whose role is to transport so large pieces that its cargo bay is way larger than the fuselage of aircraft it is derived from (I don't even know if my short list is exhaustive).

The answers of the question How are evolution and variants of aircraft considered by certification authorities? highlight that variants of an aircraft are considered as simple modification of the first type. In the case of super transporters, I imagine this is the same but:


aerodynamic obviously differs (may be especially relevant for rudder authority and engine out on take off scenario)
pressurization systems may differ (I guess those aircraft are not pressurized as airliners)
structural strength and command transmission are affected (cockpit shift, cabin floor in which cable may run suppressed, ...)


Those modifications are heavy and can affect all flight phases.

Given the Beluga XL (resp. the B747 LCF) is basically an A330 (resp. a B747) with modifications, does it share the same type certificate?
Such aircraft require separate certification. The Beluga XL has just completed its certification process.

From the Wikipedia articles you linked to:  


  The 747 LCF was granted FAA type certification on June 2, 2007.  


and


  Following a total of 335 flight hours being performed during the test program, restricted certification of the type was awarded by the European Aviation Safety Agency (EASA) in October 1995, enabling the A300-600ST "Beluga" to enter service shortly thereafter.


and


  The Beluga XL made its first flight on 19 July 2018, and received its type certification on 13 November 2019.