Fission is so much bigger then Fusion and Anti-Matter. That is mainly because Fusin doesn't use exchangers and the Turbines are so much better.

With the 25% bonus it would be nice if exchangers would be 1/4 of a reactor power, 62.5 MW instead of 50. That way you have always clean ratios. Also I think 5 turbines per exchanger are a bit much. I think 3:1 or 2:1 would be better. That way it would be 1 reactor:4 exchangers:(8 or 12) turbines. then 2 :10:(20 or 30).

https://imgur.com/jQ32ywp This two setups both have 3 GW. With the changes this would be 3 GW https://imgur.com/5MlF2Jj north with 3 turbines per exchanger, south with 2.

I don't like Koverax-enrichment. It encourages to stockpile U-235 until you have enough to start the process a few times instead of fueling the reactors. I would suggest something like the Nuclear Fuel mod does with Plutonium production from used fuel instead of enrichment. That way using the first U-235 for nuclear power doesn't hurt.

I also would set the minimum temp for fusion turbines in a way they can't be used with fission. Also should fusion produce 10k steam from 1k water? Also I think a few more in/out ports in the fusion reactor building would also be nice.