We were each other's first.
This is a serious hurdle in addition to more experienced couples opening up. You don't know how any of
you react to comming close to neither emotional nor physical intimacy, you have perhaps no idea what feelings arise when touching another person, when starting to get intimate, how falling slowly into love differs from platonic best friend ... there are so many flavours to this. You don't know your own reactions to your own intimacy, let alone to the intimacy of your partner.
In my opinion, you cannot even really know if you want polyamory, some friend-with-benefit thing, more intimacy with not necessarily any relationships expectations attached, or whatever.
What happens, if you just touch someone else in an intimate way? You don't know. Actually, you might fall in love immidiatelly, if there is some major need you hope to fulfill. You might as well get nauseated afterwards, not wanting to hear about intimacy with another for quite some time, if you run agains some limiting beliefs about sex. (Both things happened to me.)
My major concern is perhaps that without experience with early dating you are very unlikely to actually find a compatible partner, because you will jump
every possibility. Watch out for that.
I agree with what has been said about an casual encounter being useful
possibly but not entirely, and perhaps even more with small steps building up as a possible way. But in the context of experience, a to me a casual hook-up seems way to much to start with. Consider casual petting

Consider wisiting a play or cuddling party together. Consider talking with other "real-life" people about how intimacy works. Consider some form of tantra, if you are that type of person. Consider getting a close female platonic
friend first.