SnagIt videos cannot be annotated. SnagIt can only capture what is currently occurring on the screen in front of you. If you had a screen drawing application and recorded yourself drawing on the screen. It’s capable of capturing that. But the editor itself has no editing capabilities. Aside from cutting out unwanted content.
If you’re interested in creating polished videos. SnagIt’s not what you’re looking for.
In my experience, Camtasia is very good with recording computer monitors and creating videos from that content. 2560 x 1440 is my highest resolution monitor. I have two additional 1920 by 1080 monitors. I recorded up to all three of them simultaneously without issue. I cannot speak for its 4K capabilities.
And others besides what is reviewed there.