Actually, you bring up a question that has been bugging me lately.
How do you calculate where a potential bottleneck will be?
My setup is a X570, 32GB DDR4, Ryzen 7 3700x, RTX 2070 Super, and gazillions of TB of storage on stuff don't worry about it.
Right now, I can max the GPU no problem. CPU is getting there depending on what I play. RAM I have no idea how it affects game performance just everything else I do.
Is there a formula? Can I just upgrade to a 4080 Ti Super if it fits in my case and power supply? Or do I need to spend the extra 1500 updating everything else
To answer your original question: you can mainly tell by doing benchmarks and watching your CPU/GPU usage. If your CPU is maxed the whole time but your GPU is chilling at 50-60% usage while you're getting below 60 FPS, you likely have a CPU bottleneck. There are a number of free benchmarks out there, and several "AAA" games will typically have one too (Forza, Returnal, and many others) so you can tune your system.
So buying a 4080Ti without the supporting parts it needs will limit how much performance you can get out of it. Nowadays RAM typically is not the bottleneck.
Speed of ram typically isn't a problem, but ram configuration absolutely can cause a bottleneck (that usually looks like a CPU bottleneck). The amount of companies selling a "gaming PC" with one god damned stick of ram drives me crazy. Single channel ram? In 2024 my dude?
I had a Ryzen 7 1700 with a 2070 non-super until earlier this year with next to no problems. The only reason I went to a 7800x3d was because it was bottlenecking the software I used to make music.