I use this old machine but 2.4 Ghz and it works quite good.
https://www.fnac.com/mp19518259/Toshiba-Satellite-R840-16E-14-Core-i5-2430M-6-Go-RAM-640-Go-HDD/w-4
You can verify if you are in the best settings for your case (interpolation…). Try GPU but not sure it will help…
If not ok, you’ll have to wait and search for the less ressource eater editor…
Openshot kinf of worked on muy OOOOLLD precedent machine on Ubuntu. I could edit video that the machine itself could’nt read at all…