the real question is, what can you handle?
calculate by youself what can you handle in this page.
i shot my film in 4k in the GH4, 8k, 4k, 2k, hd, sd, it doesnt matter, what matters is the size of your sensor. If anyone knows different please comment.
If you see the second vídeo, the cheap iris and the chromatic aberración you talk about is from the 5000 Carlos zeiss compact prime.