4-5 3A is good, not increasing 2A is not a good idea wrt 12398. The slot of 12398 makes it one of the least prioritised trains among AC passengers.
Every composition will work fine for 12397 but not 12398. If evening slot is given then it could help in improving patronage of 12398 as well as give morning arrival at Gaya rather than odd arrival time at present.
1A is not needed at all in my opinion. 1A passenger can prefer Rajdhani.