@waifu let me know I'm misunderstanding the question, but I like to stay with original sizes only because it allows easier consistency with sticking with the art style of the game, like if your base game portrait sprite is 16x16 then you can make a 32x32 one and scale down to 16x16 but it can mean your sprite is just way more detailed and different looking

I personally find it jarring with pixel games if mod sprites look very different from how the style is in the base game

My modding experience is only with old small ass games like little fighter though, so I don't know how most modders do it nowadays