Hi and welcome to the forum, Jaxson.
For the benefit of others who may not realize the difference between shooting with the VF vs. LCD, I will provide info on this.
To me one significant thing is the difference is apparent when you are looking through the viewfinder vs via the LCD at the back of the camera. It is because when you look through the viewfinder the image is metered with a separate set of metering nodes because the mirror blocks the path to the sensor. When you take the shot, the mirror flips up and the image is taken, based on those settings. BTW, when you look through the viewfinder, even if you are using a relatively narrow aperture, what you see will be with the fully-open aperture to assist you with focusing and composition. So the aperture is closed as part of the image-recording process
In Live View mode - i.e. when using the LCD, the sensor is doing the reading, and so what you see and what the camera meters on is what will actually be recorded, including the exposure. You can demonstrate these traits by pointing the camera at a subject, looking through the viewfinder and changing the EV compensation levels. The viewfinder will show no difference, but the numbers will change, while the view from the LCD will change as you look and change the EV compensation.
While it may seem logical to stick to shooting with the LCD, that is problematic because as the weight and focal lengths of the cameras increase they will amplify any camera movement, and holding a camera like a cell phone is not a stable platform.
Instead it is much better to hold the camera tight to the eye, using the Optical Viewfinder:
This is also compounded with how the default metering works.
Metering has several different options, of which the default is Evaluative, which considers the majority of the Field of View and finds a compromise value of prioritization. To get this under control, one may have to move about the focus point, which takes time and is imprecise.
While this works for many scenes, it is not good where there is a lot of contrast and the subject is in bright light, as in the following image. In evaluative metering the system would have considered the dominant black area, thus blowing out the actual subject.
Other examples would be where the subject itself is either very dark (e.g. a black bear) or almost white (white bear). In those cases, the metering system will over-expose and underexpose the subjects respectively.
One solution to both issues it to be very precise with what is metered. To do so, one must understand that a camera's dynamic range (the capacity to include white to black and all shades in between) is much less than ours. So what we see (mediated by a lot of brain activity) will be much better than what the camera can capture.
What the sensor tries to do is configure the exposure settings for a reflectance level of mid-grey (aka 18% grey) - because colour is irrelevant in reflectance. So, the more precisely one can specify the correct level of reflectance, the more correct that exposure will be achieved and this is done by being more specific in what is metered - which is where we come to the metering modes.
I personally prefer to shoot in single point, centred metering, and lock with the * button on the back of the camera. I combine that with Back Button Focus, (assigned to the AF-ON button) which allows me to define exactly what point in the photo is the focal point. This is critical for photographing people or animals, where the eye is the critical. element.
Setting this up: you need to be in M, Av, or Tv modes to see all menu options.
Setting up Centre Point or Spot Metering: In either camera, via the menu, one can set the centre point metering as per the following from the SL3 manual:
So How does this all work:
It is better to shoot in one of the modes like Av, Tv or M, rather than the more automated modes as you have more control over the image - the more automated the mode, the less choice the operator has - the more the camera is controlling you.
1. Locate the point of mid-reflectance and lock it in with the * button
2. Locate the point of focus (e.g. an eye) and lock that by tapping the AF-ON button. (Focus should be set to Servo, so that a tap will lock focus on a stationary object, while holding the AF-ON will follow the subject)
3. Recompose and shoot.
It may seem complicated, but once you get some practise in you will do so in about a second and will have total control over both focus and exposure. BTW, You don't have to shoot in M mode - there is a fallacy that this is THE mode to work in. I, and many of my colleagues shoot in Av mode predominantly, rarely in Tv or M - but that depends somewhat on the genre.
