@Sean_H like nyrrylcadiz I'm no pro but my way of thinking about it is two fold.
First there are a lot of successful artists that work across fields, in this podcast alone they comment about working on: Picture books, board games, individual artworks to be sold as artbooks or prints at conventions, concept art etc. However I get the feeling that all of them also started by focusing on one field, for @Lee-White it was picture books but for @Will-Terry it was editorial art. As they became more skilled and experienced they started diversifying their fields and art directors had more confidence in these veterans so could offer them jobs with less visual evidence.
So to summarise start by focusing on proving yourself in one field and dream of all the others you can try once you have proven yourself.
Secondly the field you choose should be a natural fit for you and so not really compromising. This is one I struggle with and I would also love other people's take on it. I often get distracted by what I think sounds ok and workable. Such as a period when I did colouring books because they sounded like something I could do and colouring books were really popular at the time, but interest in my colouring books was luke warm and in the end I started looking for greener pastures because it wasn't something I was really invested in. At the moment my focus is on middle grade/chapter book art because I feel it is a good fit for the art I naturally tend to gravitate towards making and I feel less SCWBI artists tend to focus on it so it might not be quite as glut a market.
An exercise I was once recommended and which I still do every couple years helps me better understand where my preferences lie (This WILL change). The goal is to make a folder on your computer and save over 500 images into this folder, they all have to be images that when you looked at them you went 'this is it, this is what I want to make', it's not enough for you to respect the artist or think the art is impressive it has to be the art that most resonates with you. Then when you have your 500+ start analysing those images, what is common content? what is common purpose (book covers, concept art, stand alone illustrations etc) Once you have finished analysing you should have a better idea of where you want to head.
I hope this helps and I would love to hear other people's take on it because I can understand it feels so risky and confining to not try every possible avenue for work.