Internet speed on PC slows down drastically when the laptop is plugged into charging

The main thing I could think of to at least look into if you haven't already are:

• Update the drivers for your wireless adapter
• Find out the specific adapter in your laptop to help search forums to see if there is a known issue with it

If you need to find out what the card is you can do this by right clicking the Start menu and going to Device Manager, and then checking for it under Network Adapters

From the screenshot you provided your adapter would be "Ralink RT3290 802.11bgn Wi-Fi Adapter". So what you would typically want to do now is go to the manufacturer site for your laptop, find the model of laptop you are using on the site, and then go to the section for that model that has drivers available for your computer. Once you are there typically there is a dropdown to indicate your operating system, and then sections that contain the different types of drivers

Say for instance your laptop was an HP Elitebook 755 G2, I went to support.hp.com and put in that model in the search, and then when I was on their page for that model I went to "Drivers and Software", and put my operating system as Microsoft Windows 10 64-bit

You'll see at the bottom are the Network drivers. So for my example say I determined I was using a Broadcom Wi-Fi adapter I would know which one on the list to get. From here it'll download an executable file you can run to update the Wi-Fi drivers.

If this doesn't help, knowing the Wi-Fi adapter can still help you look into the issue. You could do different searches like "Ralink RT3290 802.11bgn Windows 10", "Ralink RT3290 802.11bgn slows when charging", "Ralink RT3290 802.11bgn Windows 10 known issues" etc. It would also help in those searches to combine it with whatever your laptop model is. So at the least you'll be able to get more useful results and you can look around to see if other people have run into that issue with your particular adapter/laptop model.