(wasn't really sure where I should put this ^^')

But I was curious on how you level the stats for twin blades, as the only guides I could find where to spam DEX until it maxes out n MAYBE a few stats into hp

For the most part, pumping DEX is pretty much how it should go for twin swords. But the idea is to have max affinity, so that does not necessarily mean you have to get 99 DEX immediately. This is especially if you have Titles and Special partner accessories to boost it. It caps at 3000 until lv100, and starts to go up as you level. MND and WIS should be useful too for your SP pool. Other than that, some people go for POW so that they can wield different weapons. And as you mentioned, some VIT is HP is nice too. Lv105 Mags do require you to be below 50% HP to make full use of the damage.

If it were me, I would go Cautious and max DEX & WIS with the rest in MND. But most people seem to put points in VIT for more HP.