The core of vegas is a decade old. Other video editors require A CPU with optimised instruction sets like SSE4, avx, avx2, as far as I know vegas pro 18 doesn't.
Magix VPX actually says it's for this reason it's so much faster
AVX-optimized algorithms Video Pro X's AVX optimizations for internal image processing and 3-way color correction make image processing much faster, deliver much more precise output quality on color conversions and free up resources for the use of additional effects.
I'm was so excited to try out V18 but I feel very disappointed .... The setup is nice but impossible to work effectively on it because of slowingless .... For me the playback must be fluent.... I guess we have to wait and see if version 18.5 or 19 vill be written in new code. .. But I honestly don't believe it will...having VPX speed in V18 would be a "killer" editing software. ..... Thanks for the feedback guys 👍