Sandwich bread density is one of those frustrating problems where everything looks right until you slice into it.

A few things stand out from your process. The 350F temperature is likely working against you. Most sandwich loaves do better at 375F or even 400F. Lower temps can leave the crumb underbaked and gummy before the outside sets properly, which reads as dense.

On the second rise, "above the pan" isn't always enough. The dough should be noticeably puffy and jiggly when you nudge the pan. If you poke it gently with a floured finger, the indent should fill back slowly. If it springs back fast, give it more time. If it doesn't spring back at all, you've gone too far. Most people underproof their second rise because they're worried about overproofing.Bread flour vs. allpurpose actually does matter here. Bread flour builds more gluten structure, which can tighten the crumb if you're not developing it fully. For a soft sandwich loaf, AP flour or even a blend works better. Some people swear by adding a tablespoon or two of vital wheat gluten to AP flour instead.Fat makes a real difference. If you're using a small amount of butter, try scaling it up. Enriched doughs with more fat (and often an egg or some milk) produce that softer, more pillowy texture commercial breads aim for. A basic pullmanstyle recipe often calls for more fat than you'd expect. One last thing worth checking is your mixing and shaping. Insufficient kneading leaves uneven gluten development. If you're kneading by hand, 10 full minutes is not excessive.