Bootcamp performance issues

This is a standard Windows driver from Microsoft/Intel - Intel Corporation - Display - 2/28/2018 12:00:00 AM - 23.20.16.4973 - not the one provided by Apple. As a check, run BCA, and download the Apple package using Action -> Download and open Bootcamp.xml, and check for the Intel driver version in that list and post the version number.

Your 13-in has an Intel GPU, unlike the 15-in models which can have dual GPUs. The AMD GPU in the newer Macs si fairly competent, but is still a mobile GPU, unlike a Desktop in iMac or iMac Pro. DPC does not show much variance, but has it in the 'yellow' zone during the test. If your performance is different on Battery vs. Power Adapter, check Power Options -> Advanced Settings and look at Processor Maximum and Minimum states.

If you re-install Windows, do not allow the Windows Updates for the GPU driver.

Can you confirm the year/model of your Mac (do not post the serial number)?

Is the FPS low for a specific game, or in general? Can you use DPC Latency Checker and test?

What are the options under Battery Settings?

Click on Change Plan Settings and you should see an Advanced Sections option. We need to check what the settings are.

You do not need to make a video. Can you check Processor Maximum and Minimum States, on battery and power.

With the current settings, speed stepping of the CPU should work normally. In some cases, such stepping can cause video jitter. It can also reduce heat. You can test, and if it behaves the same way, you can fall back to the current settings.

You can also try the High Performance setting.

This is typically due to driver implementations being different. Did the re-installation help address any performance issues?

What are the available settings under Power and Sleep?

Click on Additional Power Settings and check available settings.

What is the current GPU driver version?

Do not update the driver? If you right-click on your Desktop, is there an Intel Control Panel?

The older i5 and newer i7 come with different GPUs, so performance may not be comparable for video. Do you still have the old Mac? If yes, run the DPC on it as well.

In some cases, the Intel HD4K on my 2012 Mac provides better performance compared to newer GPUs.