As with all standard suffixes, -ish should be added to the word and made a solid word when possible.
As with many suffixes, –ish is added to words for which is was never intended, and we are left to wonder just how to make it look. I would say that readability has to be the first consideration. Add it when it works; otherwise, hyphenate it.
I think the first one is perfectly readable and would choose to make it one word. If you don’t think it is, then choose the second one.
Here I like the second one better.
When I used to ask my long-time boss, Nancy Patterson, about how something should look, she would always turn around to her trusty typewriter, begin to type, and say, “I don’t know. Let me see how it looks.” That is still probably the best advice. Thanks, Nancy.