It boost your population growth insanely.
If you got the neutral boost + all the achievement boost + some resource boost...
you can have both morale at 100% AND insanely high taxe rate
the AI is very slow at targeting morale achievements (hint hint)
Also Planet Quality impact morale, so it's much easier than it seem
PQ Boost (hability) + colonizing only large (15+) planet initially + neutral automatic availlability of planet tiles
=> gigantic planets, gigantic influence, gigantic pop growth and conpletly insane morale (did I mention the taxe income ?)
A key part in this strategy is to start off with a custom race and (yes !) the sensors technology already researched (this mean you'll spend he first 2 turn researching hyperdrive at 100% research focus ... but who cares... what's 2 turn)
instead of building colonies, you BUY factories and build ultra fast scan ship (custom design, scanners + multiple drives) once you reach 1ship/turn or at least 1/2turn you can move to a more conservative 33% research/military/social and you'll be ablle to send those fast colony ships (custom design) to those hugue worlds you found.
another side effects of having 4+ fast scan ships out there is grabbing every single anomalie for yourself (great if set to abundant)
if you're scared of the aliens you can set them to friendly, it buy you some time
but that strategy is very fast, and focusing on less worlds, but bigger, more efficient and happier mean those worlds will also be abble to churn out loads of colony ships real fast...
the poor alien will feel the grip of your iron fist culture if they try to colonize those size 10-- planets. I've seen planets flipping to my side without even lifting a finger
any game at painfull difficulty or lower is cheesecake
morale ? it's the key of the game.... that and custom built speed ships
I also love vulture ships
it's a variant of the ultra fast scout ship, but with a single low quality beam weapon. it's purpose: slaughtering constructors, freighters, transport ... anything undefended. combined with scan ships, thy are deadly (scanships are slow moving but full of scanners to scan your borders... think of it as of a slightly slow moving undefended starbase)