Pretty cool! For the Jar Models, I suggest learning how to Mark Sharps and Smooth Shade! If you are using Blender to model these, here is a quick tutorial on how to do so!
Intro
In order to achieve smooth edges and a smoother look to your model, contrary to the Low Poly look, Smooth Shading is an amazing additive to your model. It allows you to make things like edges look smooth and fluid. Marking Sharp Edges does the opposite of this. Although, when using both of these together, magic may be created!!
How to Mark Sharps
In order to mark your Sharp Edges, it is important to first understand what they are and how they work. In my interpretation, sharp edges are the edges that are chosen to be actually sharp. The marking process may come before or after you have smooth shaded, and Auto Smooth enables the feature.
How to Mark Sharps:
For your specific Model, smooth shading may be implemented in order to make the bottom and sides look smoother. Although, if you just use smooth shading, your edges will look wonky.
In order to mark sharps on the model above, select the edges that you want to be sharpened, then ctrl + e > mark sharp! Displayed below, is what I suggest marking sharp.
The edges highlighted in red, are to be Marked Sharp.
Before finalizing your sharps, firstly Smooth Shade, then on the right lower tab of your Properties in Blender, Select the Green Triangle > Normals > Auto Smooth > Enabled to 180 Percent.
Below, I will also be linking a visual tutorial on how to Mark Sharps!