Hey there. If you haven't already found a sprite artist to work with your sprites I'd be happy to help if you want to have a look over at my IG and see if you think what I have up there so far would be up for what you have in mind. (instagram.com/leafeon247)
While I do realize that not much of what I've made looks a whole lot like the polished sort of style you seem to be looking for judging by the look of the games you've listed I would like to iterate that is more because I tend to go for a rougher more loosely done look for a lot of the stuff I used to make in my own time that anything. I can try making some sample pieces in the style you want for you to look over if you're happy to let me.