In the last few years I have been doing a lot of land wildlife shooting with long lenses
For this I have tried monitor and tripod but it is not as flexible so I use a monopod and the EVF together with cage and handle
Using the EVF has several benefits
1. The OLED panel on my camera goes to 1000 cd/m2 it is very bright
2. The eyecup means no light goes it and contrast is much better than a screen
3. It is very stable as I have 4 points of contact hands, head and monopod while standing on my feet
I am not curious about using a viewfinder underwater, I have used it for photos and works well however the angle is awkward when you have to shoot low
I can see that pushing your face on the viewfinder can have some disbenefits underwater compared to a monitor however optically I think it is a superior option although of course the camera does not have all exposure tools that a monitor would have
I also think that screens and gaps of a housing greatly reduced the effectiveness of any screen
I wonder if anyone has tried the viewfinder option for underwater video I can see clear disbenefits for macro on a tripod but for that I still have the camera LCD