I only have one bird so can't offer much advice. However, from what I have read from others on the forum, whether birds get along or not is dependent on their personalities and other circumstances. In other words, these is no way of knowing if two birds will get along or not until you have both. Others with experience will come along and give you some input.
Whatever you decide, do your research and preparation first. I rehomed my grey with no research first. I have owned various animals all of my life, and didn't realize the challenges and expense of bird ownership. Things have worked out, but would have been easier for me and for Timber if I had been better prepared.
Greys, for the most part, need a lot of time and attention. Take a good look at how much time and effort you are willing to put into having a parrot before taking the leap. I don't know if the same is true for conures.
Good luck and God bless