Experiencing possibly abnormal performance issues on a Surface Pro 4 - Hardware & Software

I've had this SP4 for almost a couple years now and I've been noticing slowdown in some places. I've been wondering for the longest time whether this is "normal" when taking into consideration the specs of the SP4 (specifically the i5 model), or something I might've done to it could have caused it. The problems specifically: The pen has a delay when using it to draw/write (maybe around 0.1 seconds?). This is especially noticeable when writing fast. The programs I use a pen for mostly is OneNote and Photoshop. The delay is worse on Photoshop. Performance in Photoshop is slow. Drawing taking at least a second to register, filters taking several seconds to process, stuff like that. It's a little better when it's plugged in. Running just OneNote and drawing (just after a restart) sometimes causes the CPU to heat up and the fan to turn on. I tried looking up these issues and some owners say they're experiencing the same issues, some say everything's perfect; the pen works flawlessly, Photoshop runs flawlessly, etc. Some people also reported that their problem was solved when doing the fixes. Who do I believe? Some fixes I tried: Clean resetting the PC. (through the Windows 10 settings, I'm not sure if there's an even harder factory reset) Doing a registry edit to decrease the pen latency (source). I haven't noticed any substantial improvement and I also have no hard evidence to what editing those registry keys actually does. Disabling the pen cursor (source). Disabling handwriting recognition in OneNote 2016. Disabling flicks and all the other pen gestures you can find in the legacy Pen & Touch settings. This can be found through the legacy Control Panel. Using a registry edit to add the 1368x912 resolution (25% of the SP4's screen resolution), and using that instead (source). Creating a custom power plan. Apparently this fixed the performance issues for someone. Other things: I'm in the Insider Program, so I've been on preview builds of Windows for awhile now. I recently tried dual booting Linux, which involved partitioning the built-in SSD and changing the boot order through the BIOS. It worked but I ended up reverting everything. Not sure if that might've caused anything. A spec comparison between all the iterations of the Surface Pen (and how well they work with every SP model) I'm just looking for some peace of mind. If you have a suggestion that you think could help that would be great, but if it's just the hardware in the SP4 showing its age, then please let me know so I can finally stop looking for solutions.

I had some significant performance and battery life issues back when I had a Surface Pro 3, and it was mostly because of Windows Update apparently being stuck, although that was on Windows 8.1. How do the updates look?

The Insider Program usually tests Surface drivers. If you revert to retail Win10 that might fix things. as for the Pen, are you using the older Pen or the 2017 redesigned one? the 2017 is meant for the SP5 and Book 2, but it should work fine.

Preview builds caused me a lot of problems with my surface to a point where I was getting slowness and BSODs from time to time, I suggest you either stay away preview builds or use the slow ring. When I had some serious abnormal unfix-able issues, internal clean reset didn't help but installing windows 10 from a USB flash disk did the trick. Try that perhaps? I believe that preview and fast builds aren't tested on surface devices, so stability is not guaranteed.

What's your full specs? If you're on the i5 4GB with a filled up SSD, I wouldn't be surprised at some slowdown.

It's on Windows 10 version 1809. It lists updates KB4464455 (there's no page for it) and KB4462930. I'm using the SP4 pen. I considered picking up the 2017 one except I heard that pen has issues of its own when you use it with a SP4. IIRC I believe I tried installing Windows through a USB before with no results but I'll try it again later. It is indeed the i5 4GB model. I made a second partition on my SSD of around 5GB for Google Drive syncing. The main partition is about 75% full.