To the OP, this is the problem i was and still am having.
Im playing BF4 at 1440p and between 110 to 145 fps. I see this through a 144hz monitor so its lovely and smooth.
Unfortunstely using the nvenc codec to record through obs yields every 7th to 10th frame (when viewed in premiere pro) as a duplicated frame. This makes my "60 fps" recording feel like its a badly done 30 fps recording. It feels stuttery and bad. Whats frustrating is that lowering the bitrate of nvenc does not improve things. Its the rendering stage which is choking us both out.
I note that Lvlcap, a 2million subscriber youtuber posted here with the same issue. His rig is crushingly powerful so this isnt going to improve, and he appeared to give up in the thread on obs being his solution.
Unless someone has a solution, im doing this:
I wanted obs because of its ability to allow me to record multiple audio tracks. This element works very well resulting in 3 tracks for me (game, my mic and Teamspeak3) all synced up perfectly (syncing seperate audio is a big pain in the behind) and more importantly able to be brought into premiere as seperate but synced tracks i can adjust and edit seperately in videos.
So given obs just cant deliver smooth (non frame duplucated), 60fps 1440p video at bitrates around 50-70000 kbs (which shadowplay can do easily) i am now:
Using obs to capture my 3 audio tracks with the "eye" on the scene off. Tjiscway i get an mp4 with my synched audio tracks but no video.
Using shadowplay to record 1440p 60fos video with no audio.
Pull them both into premiere and just sync the ingame bud to ingame audio and its all sorted.
I really hoped obs woukd be a 1 stop shop but it seems not :(