Here are some top big and tall office chairs with a 500lb capacity and adjustable features:

1. BOWTHY Big and Tall Office Chair – High back, adjustable lumbar support, PU leather, heavy-duty steel base.

2. HeroSet Ergonomic Chair – Wide seat, comfy padded cushion, adjustable lumbar, PU leather.

3. Vinsetto Office Chair – Wide seat, ergonomic linen-style fabric, height adjustable, swivel wheels.

4. Flexispot OC3B Mesh Chair – Breathable mesh, padded headrest, adjustable lumbar support.

5. SIHOO M18 Ergonomic Chair – Mesh design, adjustable lumbar, contoured cushion, padded headrest.

Let me know if you need more details!