No worries man, this is the best laid out directions even though it’s a few years old everything still applies just plug in the numbers for the newer strips using their formulas. They got a lot more efficient in the last few years so the Gen 3 are worth the extra money:
And this is the massive LED strip DIY build discussion thread here, to make it more manageable I’d sort for messages from @Gpaw@ReikoX or the OP, @Mr.Sparkle