A British person can weigh in about British usage, but in American English, 'loll about/around' is not very common to hear; I would associate 'loll' in American usage to have a greater connotation with frivolousness, laziness, wasting time, inefficiency. Whereas, 'lounge' has a more neutral connotation of just relaxing, resting, enjoying yourself, etc. 'He needs to get back to work and stop lolling around.' 'Lounging around' could also have a negative connotation but would be more dependent on context.