I am looking at several objects in my viewport and all of them are of different sizes.
For example, a new mesh cube has sides that are 2 meters (I already set the units to metric)
However, when I go to the Object settings for these objects, the Scale is always 1.0 for every single object. (the scale is relative to original size)
But I want to use a system where I can type 1,1 METERS (or feet) instead of this "percentage" system.
How can this be done?
I think you confuse the term scale with dimension. Changing the scale is always a percentage value of the object's size. If your cube is 2 [whateverunit] and you type "S - 1.1" it now has 2 [whateverunit] multiplied by 1.1
The only method of changing an object's size directly without using percentages I know of is manipulating its dimensions which you can find directly below the scale settings in the properties shelf. AFAIK there are no keyboard shortcuts to manipulate the dimension values directly - maybe due to the fact that Blender never intended to be an accurate CAD-like software.
As mentioned, in Object Mode, there is a "Dimensions" panel, directly under the "Scale" panel in the object transform sidebar, that shows the total dimensions in world units.
Additionally, in Mesh Edit Mode, near the bottom of the right sidebar is a section titled "Mesh Display". At the bottom of that section is "Edge Info" with a checkbox for "Length". You can enable this Length checkbox to see the lengths of individual selected edges in your model. I've found this quite helpful to see lengths of individual pieces of a complex object.
In the properties shelf (activated by the N key in the 3D viewport) in object mode, one of the four transform types in the top pane, is labeled "scale". You can enter specific values there with a pretty good precision. However, these are still percentage values. There is an analogous panel in the properties editor under the object context tab. These are also percentage values.
Note though that you can take advantage of the ability to use a regular expression to achieve a degree of precision in entering scale values. Suppose that you have an object which has a dimension of 73 units, and you want that same dimension scaled to 87 units. After you select your method of entry, whether using the S key, or by entering the values in one of the panels I mentioned above, you can enter the string ( 8 7 / 7 6 ), which will be interpreted as an expression to scale the dimension by 87 / 76 thx, providing you an exact dimension.
