I use Cinegy Daniel2 codec for editing in Premiere Pro. This codec take more space on disk, but work veeeeery fast compare to H264. Also it work more fast for me compare to ProRes.
Cinegy Daniel2 can be replaced with DNxHD MXF OP1a or MXF OP1a. Try these codecs. In Premiere it works very good.
You can convert all your raw files to one of this codecs before work, and then you will have more smooth workflow.
With this codec I could edit multicam 4K video with more than 3 cameras and it worked smoothly.
I have i7-4770K, 24gb RAM and GTX970 GPU. It's a PC from 2013 year (approx).
Also you can convert your videos to lower resolution and link them in Premiere Pro as Proxy files. Then you will edit files with proxy preview, but when you will render them, Premiere will use original full resolution files. When you need you can switch in one click between proxy and original resolution files.
For better understanding you can goole "Premiere work with Proxy files", "Premiere Cinegy Daniel 2", "Editing codecs for Adobe Premiere".
I can't google for you, because I will have most of materials in Russian.
Link to Cinegy Daniel 2 codec.