There's no concrete yes/no answer, it depends on the game you play so much as well.

Some games are really CPU heavy and that will be your bottleneck if there is one, others are primarily GPU heavy and won't rely on the CPU as much.

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.

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.

Just get a 5700x3D