My source: veekun
(I used to refer to Marriland, but it was too clogged up with a lot of sidebars IMO). I might've overlooked a few things, because I skimmed, not examined, so do point out and correct my mistakes.
Some research backstory
First, I started off with pseudo-legedaries (Dragonite, Salamence, Metagross, Grachomp, Hydreigon) and found 2 things - that all lineages have 300 - 420 - 600 BST (so many have noticed too), and that they all increase their stats between evolutions in multiples of 10, not 5 (eg. 58 - 68 - 108 for Garchomp line's HP, but I could not find any with, say, 40 - 55 - 90).
Secondly, I turned to Bug-types, but found a depressing recurring pattern - for 3-form evolutions, most 2nd stages are as slow as, if not slower than, the 1st stage LCs (damn them all metamorphosis lines). Being pseudo-legendary, Aurumoth could break the mold, but this means Speed stat for my 2nd stage would be severely restricted.
Lastly, I moved to Psychic-typings. There I based Aurumoth line on the Reuniclus line, where there is a significant pattern - its strongest stat is already very powerful even when unevolved, while its remaining stats gradually fill out to help it achieve full potential. Therefore I decide to focus heavily on its Defense stat, turning it into an angel-spawn (I would've liked to put the adjective "fluffy" there, but I fear it constitutes the PJ word.)
Unfortunately the 1st criteria (pseudo-legend) limits a lot in terms of competitive play, so I had to make do with what was given. Still, I've manage to give as good a shot as I can (15-minute crash course on BSR is neither fun nor enlightening at all, I can attest to it).
And thus I present to thee: LC > NFE > AURUMOTH
<Birkal> if pwnemon was my little brother, I would beat some sense into him
<Birkal> and then take him out for tea and scones
<Birkal> and then we'd talk ASB and grow facial hair together
<Birkal> like proper brothers
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