Premiere Pro Playback Issues

First of all, I wish you all a good day.

Let's proceed to my problem. I am working with this on daily basis. When "editing" I don't really apply any LUTs or some special effects, all I do is square masking the webcam (in opacity), throwing it's layer on top of the gameplay and then hundreds of cuts. That's when the real show starts! 
after 10 minutes(of "edited" video), 50 cuts. I press the Space, Premiere won't start the playback for about 3 seconds, then it starts. 
25 minutes, 80-100 cuts. I press space, Premiere won't start the playback for like 10 seconds.
At this point, when I pause the playback, press C, hold shift and click so I do some more cuts, timeline and whole Premiere gets laggy for a moment and after that I have to wait like 10 seconds for playback. 
"Yeah, 10 seconds, that's nothing." It may be, but when you  multiply it by at least hundred times, it is quite some pain. 

One thing I've seen in task manager was my CPU getting up from like 20% to 65% utilization right at the time between me pressing the Spacebar and playback starting to play.

I tried pre-render whole timeline, after the 25th or so minute mark, so I could cut things more easily, but it didn't really help. 



Client sends footage from OBS,
Webcam 1280x720 and 50fps [Roughly 5Mbps bitrate, H264(High @L370_2.2)]
Gameplay or screen in general is 1920x1080 and 60fps [Roughly 7Mbps, H264(High @9552317.2)]

My PC Specs: 
AMD Ryzen 5 3600
nVidia GTX 1070
32GB RAM (2x16gb 3200mhz cl 16)
M.2 SSD


Any ideas what should I do with it?