Is it possible to get a 4k demo? I use the mac version. I want to try if the 4k cips work well on my mac.

I don't think that's possible. I'm not an expert on how the download process works, but here is my best guess. I think demos are downloaded in your default size. If you don't have premium, you can't set the default size to 4K. Maybe you could play a 4K demo if someone emailed you both the models and data folders, but I don't know and that would probably ***** the user terms and conditions.

On the positive side, I can probably help answer your question. I run on a 2013 Mac Pro with 3 displays. The largest is a 4K 43" display. On that display the 4K cards are noticeably better than the 3K cards. My second display is a 30" 2560 X 1600 display. On that display the 4K cards and little better than the 3K. My conclusion is that if you have a 4K display, the larger the better, then 4K cards look better. With a smaller display, not so much.

Access to 4K resolution is Limited to Premium members only.
The Most resource demanding clip type is the Table clips.

Through my testing ( on windows 10 os )
4K table clips require about 15% more CPU resources than it's 3K counterpart.
and about 45% more Memory than it's 3K counterpart.

This is e1212 side by side
left is 3K size clips, right is 4K sized clips