Slow performance with external M.2 SSD

Hi,

I have a work macbook pro m1 PRO 2021, it has 16gb ram.

One on of the project i'm working with 5K red files, 6K braw files and exported mp4 files. I bought an M.2 ssd 2tb so that i can edit on that. But now i'm facing a lag in the edit.

I noticed that when I had the red file open in the preview window, as soon i play a video on the timeline things started to lag. Is this lag happening because the mac doesn't has enough ram to keep the preview while i'm playing a clip on the timeline or is the the GPU? 

with de BM 6K files, i don't have that problem, its only with the red files. 

if its indeed the ram, then i know next time to ask for more ram, i just forgot to inform my bos to get a minium 32gb ram.