Mubālaghah intensifies the claimed degree of a quality. Tajrīd imagines an additional bearer of that quality drawn from its original possessor.
Compare:
“So-and-so is very generous” — straightforward intensification.
“There is a sea of generosity within him” — tajrīd may be the relevant effect.
“Even the seas would fall short of his generosity” — the hyperbolic effect dominates.
An actual passage may combine figures; each needs a distinct justification based on its precise wording and context.