Solutions for lag?

I've got some brush lag! generally it runs okay, but the longer the program is open i notice it lags more, the brush starts to look not as smooth. it can be very hard because I tend to make fast strokes, when sketching or whatever. so when the brush lags, freezes etc. it gets in the way! i've tried a good amount of solutions to fix the lag, ill try to remember and name them all. but they haven't really fixed the occasional freeze of the brush or laggy-ness in general when sketching fast.

https://imgur.com/95F4oLD This screen shot is what tends to happen a lot, it freezes a lot and makes a sudden stroke which is a straight line. where i have to constantly ctrl+z
Or when i'm in a painting stage which more layers, the brush just seems to lose its quality and get kinda laggy and jagged..

What i can remember i tried that didn't really change the freezing/brush lag etc:
legacy compositing check on, tried both use graphics processor checked and unchecked.(<-- it doesn't seem to make a difference either way, but when its off the quality looks bad, i don't really know if its helps. so i may just keep it on) cache tile size to lowest, cache levels to lowest, (<-- i would go for 1, but it wont let me) history states low, (<--set to 20, idk if i could make it lower and if it'll make any big difference) memory i let photoshop use: i've tried 80%, and i've gone lower, i don't actually know if higher or lower makes it lag..., drawing mode: basic, use graphics processor to accelerate computation on and off, use openCL on and off, (<-- these both don't seem to make a huge difference, but i couldn't tell which one is better) Also deleting all PS default brushes since i don't use em, turn smoothing OFF

That's all i can remember that i've tested! honestly hopefully i did something wrong so i can fix this heckin lag!

Drawing at a lower dpi should help reduce lag right? Although i'm not sure how low to go. because although i don't know much about dpi, i keep it at 300 usually. i don't know how low is too low, to where the quality gets messed up, or i cant put as much detail into it etc.. i'm testing out 250 dpi in the link above. still lags the same. so i'm not sure if its worth going lower dpi or just stick with 300 dpi and find another solution.