Question I7 - 9700KF, 16GB 2666Mhz Ram, RTX2070

[garryExtreme!19]

Playing Fornite FPS Should be stable at 270 but keep dropping 190, 126, 116, 79

what could be the reason.

Tried new motherboard, new cpu still dropping is it normal. I do stream as well along with playing. I have no idea it should be stable or not. my friends saying there FPS is constant at 240.
I am using Acer 144hz 1ms Full hd monitor with Dispaly port cable.

 

[BeauJet]

Your screen, the settings of the game, and what's cooling your gpu(And if overclocked at settings higher than average can cause stutters.) These drops can be natural for loading in new protoins of map, plus your streaming which tasks the machine even further.

 

[TerryLaze]

Tried new motherboard, new cpu still dropping is it normal. I do stream as well along with playing.

If you use your CPU for streaming then that's the problem fortnite is not made for multitasking and freaks out if anything else uses the CPU extensively.
Use a FPS limit close to the 144Hz you get or even better use your GPU for streaming that way you can stream at full FPS.