You can’t just pre-compose into a 25fps comp because of the particle interpolation problem…
Option 01 (pretty good):
Save your Ram Preview and it will only save rendered frames and you can then change the frame rate to 25 on re-import.
You may want to change your comp to 75fps so you can easily change the new frame rate to 25 without any math problems.
Option 02 (better):
Change your comp frame rate to 75 which is easily divisible by 25. Then nest your comp into another blank comp at the original 75fps, then use the TimeWarp Filter on the comp, change to “Whole Frames” and set the speed to 300. Now your comp is still 75fps but your animation is sped up 300 percent and will play back correctly at 25fps. Change the render settings to use 25fps instead of the comps 75.