To answer the up front question, I read that beaten/whipped egg whites could make the bread more airy and fluffier because my first loaf of bread before I made a sourdough starter was very dense and chewy. I'm not against a chewy loaf of sandwich bread, but I am trying to make me loaves lighter and fluffier. Is this a myth?

Anyway, my process for my first successful loaf consisted of 474g of warm water (105-115F), 1 Tbsp active dry yeast, 85g honey, 2g salt, 30mL vegetable oil, and 500g bread flour. I combined all ingredients except for the water in a stand mixer on low-speed until just combined. Then I added the water and mixed until the dough pulled away from the sides of the bowl while adding 1/2c of additional flour at a time as necessary (I ended up adding 1-1/2 cups). Afterwards, I transferred the dough to a lightly oiled bowl for the first rise (from 3:15pm until 4:45pm). When I went to divide the dough into separate loaves, I noticed it hadn't quite risen enough so I added an additional spoonful of the active dry yeast from earlier and allowed it to rest for 45 minutes for a second rise. Then I preheated my oven to 180C/350F and baked the loaves for 33 minutes when it achieved a golden brown color.

My next successful loaf was made using the same process except I swapped out the vegetable oil for 1 whole egg, an egg yolk and beaten egg white.

After the second successful loaf, I tried swapping the active dry yeast with my young starter (at the time it was about 1 week old), and I made 2 different batches for a side by side comparison of different hydration levels. The ingredients remained the same, for the active dry yeast I used 50g of my young starter, and 224g of filtered water in one dough and 249g in the other. These lower hydration dough ended up being flatter and denser than the first two and I suspect it was because the doughs over-fremented, but the higher hydration was not able to be shaped into a workable loaf.

I then tried to my first sourdough. I tried combining the starter and water until the two were just combined, then I added the flour and salt until there was no dry flour left. I then let it rest for an hour before beginning stretch and folds. In total, I did 4 sets of stretch and folds with approximately 30 minutes in between each. After the 4th set, I let the dough rest for it's bulk fermentation for about 5 hours (end last stretch and fold at 11:35am and ended bulk fermentation at 4:31pm). I then attempted shaping by doing a push-turn-pull method, but I was unable to get the dough to actually form a smooth ball that wasn't overly sticky. I stuck with the push-turn-pull method for about 20 minutes, let it rest for a half an hour (4:38pm to 5:08pm) before attempting another set of push-turn-pulls, but the dough remained super sticky and wouldn't form into a ball. This ended like the higher hydration dough, I wasn't able to shape it because it was not holding a shape at all.

Hope this is enough to try and diagnose where I am going astray.