Unless you can find a local meetup then trying before you buy isn't very easy, sadly. You can do things like print out layouts from https://compare.splitkb.com/ which will give an indication of how well a given design fits your needs, but nothing is a substitute for using it for a while. Even trying something out for a few minutes won't really give you an idea of what it's like to live with day-to-day.
Many of us have just taken to trial by fire, buy things based on hunches and work from there, but that's not an easy pill to swallow in terms of the financial burden of doing discovery that way.
Good luck in your search, be sure to scroll the posts here and in the reddit for inspiration.