Based on a test system, AMD A8 @ 1.9 GHz with a similar configuration, if anything, 10 was slightly faster than 8.1, subjectively. It's more than likely that the junk (sorry enhancements) that are on the machine is what is slowing it down. Have you checked what is actually running and how much of it you need? Google how to clean it up if not.
If you still want to try, your best bet would be to contact Acer and ask what a factory system restore disk or disks would cost to restore the system to "as shipped". It will come with all the drivers you need and an OEM product key built in. But remember to make a note of any product keys for your application software before you restore it, since at some point the disk will be wiped. If you don't have the keys, download and install Belarc Advisor (free) run it and it will identify your keys.
If you want to try without committing any cash, you could use the USB drive you have to install Win 8.1 to check - BUT - depending where you got it from, you may need to find all the drivers for it - try the Acer site. If you have 16 GB free on your hard drive, you could spin it off as a temporary second partition and install there without messing up your Win10. Depending on your comfort level, you may need help with this.
One almost guaranteed way to speed up the system would be to replace the HDD with a SSD. I've yet to see a system that it didn't help. The smaller ones (128 GB) are becoming affordable but would present a challenge for your data, if you have a lot.
I'd certainly have a go at cleaning up first, it's the minimum cost option.