Disk Space Strategy

As you find from my signature I have no power machine for my video editing. Since I'm doing only small projects and I'm amateur, I get along OK with it. No plans to invest here.
One thing that puzzles me though. As I have only a 1 TB internal SDD and want to keep space free as I'm working also with PS and Lightroom, I put my current project (540 files, 45 GB) on an external SSD (Samsung PT500B, USB 3). Running the BM Speed Test app I found that read/write is significantly slower with the external SSD:

External: read 370, write 420 MB/s
Internal: read 950, write 1000 MB/s

Before I move all the files back to my internal drive: Will using the internal drive increase the performance of editing in Resolve (edit, color, no Fusion, only little FX)? I just started video editing and have no comparison what's fast, what's slow... What's a good strategy for my environment, taking into account that I don't want to spend a lot of money for a new (faster) external drive and say I want to keep around 100-150 GB free on my 1 TB internal SSD?

Thanks for your input,
Oli