I would also be interested to know the difference, after a google it seems that FA Meringue changed at some point from being predominately egg-whites and sugar to a cooked meringue with caramelised notes.
In regards to the Humo eLiquid there is definitely no cooked, caramel or bakery notes as such, as said it's purely egg-whites, sugar and lemon.
I did a quick test with FA Meringue at 4%, Lemon Sicily at 2% and Sweetener at 2% and although there were some similarities on the nose it didn't strike me as a possibility that these are the flavours used.
FA Meringue possibly, although as I expected, 4% is way too much. Lemon Sicily at 2% didn't bare any resemblance to the original and apart from dropping it down to 0.5% and testing again I think it's futile. The striking difference was the sweetness, using 2% sweetener would usually be a lot for me but in comparison the Humo liquid tastes 10x sweeter, they're definitely using something to mimic the taste of real granulated white sugar, possibly a mix of Cotton Candy and Sucralose?
Humo actually lists 'sugar' in the flavour profile for their Lemon Meringue eLiquid.