Quickest way to transcode many 4K video clips to be playable

Server Version#:4.114.3
Player Version#:

I have many 4k videos we have taken mostly around 3 mins but some up to 30 mins.
I have them all in the library now in original form.
What is the quickest way to get them all converted so they play seamlessly on my PCs etc?

Thanks

With a Plex Pass, the Optimize feature of Plex.
Without, Handbrake.fr or similar software.

Thank you.
Now have a year Pass.
Seems good now. Thanks again