<p>Recently, my Ender 3D Pro has been unable to print any large models successfully with PLA as the filament starts to expand inside the Teflon tube, causing a clog after about an hour of printing. I am starting to suspect that the problem is heat creep.</p>
<ul>
<li>This occurs with the two brands of PLA filament that I use (3D Fila and Voolt 3D).</li>
<li>The hotend that I am using is the one that comes with the printer, I don't know what it is made out of.</li>
</ul>
<p>I have tried many things to patch this problem:</p>
<ul>
<li>Try to unclog it with the needle</li>
<li>Replace nozzle (three times)</li>
<li>Check if the Teflon tube is touching the nozzle</li>
<li>Increase temperature from 200 to 220 °C</li>
<li>Increase temperature from 200 to 215 °C</li>
</ul>
<p>If the problem is indeed heat creep, I have plans to control the heat sink temperature with a Peltier and an extra thermometer. Any other ideas are appreciated.</p>

This sounds like heat creep may be the problem. For preventing heat creep to occur you should do the opposite, print at lower temperature, tweak retraction length and increase cooling of the cold end.
A Peltier element is not very effective cooler, use a bigger fan, or a fan with a higher flow rate. Note that the Peltier element required a large cooling body and a fan as well, so this adds a lot of weight to and limits space of the hotend. You should not go there, it has been tried before.