I don't think you will be able to record in anything above 120fps Without a dedicated graphics card Or get a ryzen apu
tbh i dont know what your talking about well usually when i play with forge with like 9 mods i dont usually get 240fps but then i accidentally clicked on optifine alone and now i easily get around 200-400 its around 100-200 when recording , im still trying to get the best settings for it to work smoothly my specs: i7 gtx 960 8gb ram, if you have anything above that or similar you can easily record in 240
I have worse specs than that and I can record in 360fps no problem but if you want to have the best renders you have to get above 240 fps when recording
i heard it also depends on space, anyways it doesnt really bother me that much , i dont really play this game often