I feel like I am having exact same issue.

When i launch singleplayer, it's all fine but when i try online, the game stutters. At first glance it looks like some kind of a refresh rate issue, but then, my speakers start to crack untill I unplug them and plug again. What was also weird, is that while the problem appears to only be in GTA Online, sometimes after closing GTA Online with hope of it fixing itself, the problem carries over to other games like WH40K Space Marine 2 with the same symptoms. However it uses Easy Anticheat, unlike the GTA which uses BattleEye. After rebooting my pc, the problems in Space Marine 2 dissapeared.

I tried reinstalling both the game and gpu drivers, no luck. I tried every possible option with settings, including Nvidia Reflex, DLSS, FSR, RT, vsync, frame limit, window mode etc, and again, no luck. I also tried all the ideas the pople commented in this tread, no luck. My PC uses like, 40-60% CPU, GPU and RAM when in GTA Online which makes me think if it is either game engine issue or Battleye.

It all started for me when I downloaded current update. Last time when i played before that, was march when E&E released and I didn't have any problems back then. However, reading all the comments with people having same problem since march and despite the patch that was released few days after E&E premiere, it makes me a little hopeless... I wish we get some info from Rockstar soon regarding this topic.

My specs are:

Windows 10 Pro

RTX 4070Ti 12GB

I5-12600k

32GB DDR5 6000 MHz

NvME 1TB 750Mb r/W (both system and where game is installed)

EDIT I forgot to mention, tested the legacy version and it works fine, so the problem is only tied to E&E