Hard to know without mentioning games played or settings used.
The way you determine bottlenecks is running MSI Afterburner with CPU and GPU usage enabled to show onscreen while playing. This value will show as a percentage onscreen in the CPU or GPU row. Also, don't go by in game benchmarks when comparing CPU and GPU usage. The in game benches will almost always show a different ratio form actual gameplay.
For the most part, the 8100 and 1070 Ti are not so unbalanced that they can't produce smooth gameplay, but you may need to lower settings in some games to raise CPU usage.
The following video shows this in Ghost Recon Wildlands, the last of the several games benched. That said, some games, including GRW and almost ALL of Ubi's games, tend to be prone to frame rate fluctuation and hitching. I have played GRW tons, and even on my 8700k, 1080 spec, it hitches sometimes. Usually reloading the safehouse you start at via fast traveling back to it, and/or waiting 10 - 20 seconds for textures to load in, alleviates it. Traveling through new areas of the map in GRW though, especially while map details are becoming visible, usually involves some amount of hitching. Even once the map is clear, you will likely still get at least some hitching your first time through a mission.
Developers like Ubisoft cram in tons of eye candy graphics on outdated game engines. It's not always the hardware you're using.
[video="https://www.youtube.com/watch?v=sYUfEKSkMBY"][/video]