The drivers SHOULD be functionally identical between the two. My best advice is to either use a trial of or purchase Acronis True Image, BACKUP THE ENTIRE DRIVE [so as to be able to restore it later if you have any issue] and then attempt a clean install of Win 8.1
The only potential issue you may run into is valid program licensing [as I strongly suspect your Win10 License won't work for Win 8.1.
Really? I've only run it on my desktop [came free with my SSD] but it didn't SEEM overly resource heavy...Acronis chokes on the Surface
You may only find there is a problem when you need it. Do a test to make certain it's working. A few people have claimed it won't on the Surface tablets. Those same people, for the most part, said Macrium did not have the same issues.Really? I've only run it on my desktop [came free with my SSD] but it didn't SEEM overly resource heavy...
I am using my sP4 in a dualboot with Win8.1/Win10.
I backed up my Surface Pro drive using Storagecraft Shadowprotect then restored it to my Surface Pro 4. Win8.1 is working and I get ane xtra 1-1.5hr battery life.
It booted up with a standard VGA driver, and 5-6 drivers with an exclamation mark. I fixed those by downloading the full SP4 Win10 driver ZIP file from Microsoft's support site, clicking on each with a (!) and manually selecting the path I unzipped the ZIP file to.