I have a 32 Flex so close to your size tank.
Currently, there is a RG, clown pair, McCoskers wrasse, and a Citron clown goby. My wife really wants a mandarin, but I'm hesitant with the whole pod thing unless we breed our own. For my tank and RG specifically, he was the first fish added and is definitely king of the tank although nothing too crazy. The goby is always hanging out in his areas and the Gramma didn't like it at first, but despite all of the body shakes and open mouth tantrums, the goby showed he ain't playing no games and wouldn't budge lol Now the RG doesn't care.
The wrasse is the only other fish to enter the RG's domain and is occasionally chased off. When the wrasse was first introduced, the RG was constantly chasing him around no matter where in the water column he was in for the first month. I had to take the RG out for a month and then dropped him back in. So far, so good nearly 4 months later.
I would say it depends on the particular fish, but it could be fine. I'd personally add the mandarin first and let it establish itself for a couple months and then add the RG. Later down the road if the RG decides he doesn't like the mandarin, take the RG out for at least a couple weeks and try again.