I have demoed the fx500 before buying the TC99 recently. I think the TC99 is equally as powerfull but has a lower launch angle and is much more controlled. I found the fx500 to be a bit erratic..
The TC97 would be more simillar to a radical pro. I dont know if thats the beste comparison though, I have only ever hit a couple of shots with the radical so cant say much about it. To me the TC97 is like what I would imagine a pro stock blade to feel like or a it could be compared to a more whippy Pro staff 97.
The Angell string patterns are a big factor in how they play. The 16/19 is very open, lots of spin and high launch and give some extra power. The 18/20 is the total opposite its one of the tightest patterns out there, lots of control but you lose out on spin and power.
I would say if you enjoy the launch angle of your fx500 the TC97 16/19 would be similar in that regard. A bit more predictable and control and probably a smidge less free power.
The TC97 18/20 is a control frame through and through and much closer to the radical pro. Feel is very different and they are not that similar i guess, but just speaking in terms of control and power.
The TC99 is my personal choice, so there is a bias probably

but to me it is the best of both worlds. Lots of power like the fx500 but very good control.