The DH Ghost engine wasn’t much larger or heavier than the Goblin. It did burn more fuel to make its power, though, and the Venom was hoped to have range similar to the Vampire, which is part of why the wing tip tanks were fitted–also, like the extra fuselage tanks on the Hawker Tempest vs the Typhoon, the Venom’s thinner wing couldn’t hold the same tankage as the Vampire.

The big disadvantage that the Ghost had was that the R-R Nene was slightly smaller and made about the same power–the RD-45/VK-1 engines in the MiG-15 were Nene derivatives. But the Ghost was a DH product, and DH wanted their own 5000lb thrust-class engine, and it meant that the Vampire airframe could be used without much modification. Of course, the wing LE sweep back might be due to shift in CG because of fuel tank rearrangement, but it might be due to compressibility at low alt. or to accommodate the changed control surfaces that the Venom used.

I’d argue for compressibility because the Nene-engined Vampires (the Sud-Est Mistral and the Australian F.30 Vampires) topped out at about 570-580mph tops, and that’s for the Mistral, which lacked the “elephant ear” intakes that the F.30 and DH’s own experimental Mk 2 Vampires had (where were Mk1 and Mk3 airframes converted to use the Nene), while the Venom had the same power, but topped out at 640mph.