I wear a size 14/16 or xl/xxl; what size would be best?

Hii!! I have about the same measurements as you and I got a size medium. Hope this helps :))

I am 5' & 185lbs should I get a large?

Dear, we suggest you can try 2X-Large/3X-Large.

How supportive is the bra ?

I'm 32DD and there's no support, had to wear with my bra underneath if I want my chest to stay put otherwise it's OK on those non-work related days for me. Wish it did come in smaller size. I sized down 2 sizes.

Does anyone actually own skims to verify how good of a dupe this is? am thinking about buying but don't want to be disappointed

Skims sizing runs small compare to this. This bodysuit has a hook eye closure in the crotch area while skims are the snap ons. I prefer this hook as it's definitely easier to close, I was struggling more with the skims. The only thing is, skims' has better chest compression (where I like how my chest look) while this one has none. Overall, I would pick this one compare to skims, but I only bought mine this Feb and the seams are coming off by middle chest area already. I do wear it 4-5 days a week, will definitely stock up.