Pre-Transcoding, which format/options should i pick?

So I’m looking to move my Plex Media Server to a 2009 Mac Mini that i have lying around.
It can handle 2 1080p streams transcoding but to make things easier I’m looking to pre transcode all of my media.

The question is which ‘optimise’ option should i use?
The client devices i have are iPhones, iPads, Apple TV’s and a couple of iMacs.

Clearly they are all apple devices so they all support they same formats but the only options in plex are for iOS or Universal TV/Universal Mobile…

Which options under ‘optimise’ would allow for direct play across all these devices?
(I wish you could just pick H.264 or H.265…)

Any help would be amazing! Thanks!!!

I use MKV with h264, 1st audio 2 channel AAC, 2nd audio AC3/DTS/etc., only forced subtitles in srt format. For devices that want MP4 the container change has a near 0 impact on the server.

Thanks for the reply.
So do you optimise your media outside of plex with something like handbrake?
Or do you use Plex’s ‘optimise’ feature to do it for you?