Personally I use this viewfinder which is a high-resolution electronic viewfinder, that can be mounted onto the accessory shoe on M and X cameras. It has a 1.4 MP resolution, and can be tilted upwards 90°, which makes you work from a very low angle.
All exposure parameters are shown in the viewfinder, when attached to the camera.
It fits onto the following Leica Cameras:
M (Typ 240)
M-P (Typ 240)
M-E (Typ 240)
M Monochrom (Typ 246)
X2
X Vario (Typ 107)
Setting up the Leica EVF2 on the Leica M 246
It's pretty easy to set up the EVF2 on your camera. Start by setting the focus aid in the menu to "Automatic" in the camera and then mount the EVF-2.
When you touch the focusing ring on the lens, the preview comes up in the EVF-2. Notice that in the upper right corner it says 1X. So you have to use the thumb wheel to change that to 5X or 10X.
Viewfinder vs EVF-2 on the Leica M 246?
Using the EVF-2 is very precise to focus with, but the analogue viewfinder is much faster and more intuitive for shooting. You will have to try it out. But do try the EVF-2 because you are missing out if you don't know about it.