I would just like to add a small correction (if allowed) regarding the numbers you've provided, because I think the scale of the Famine is important to the question of life before it. Ireland's populaton before the Famine is generally thought to have been 8.2 million, not 9 million, and the population of the entire island (not just the Republic) in 2018 is 6.73 million, not 4 million.

Can you clarify what you mean by what was it like? Economy, politics, society and culture etc?

I'd be interested in how it colored everything, before and after.

Like, were the writers, painters and other artists upbeat and cheerful before, but dark and brooding after? Did it cause changes in marriage rates? etc.