It's up to your own judgement about you and your ride and you will get a huge range of opinions. Traffic laws more or less apply to bicycle riders with specific exceptions, but a lot of times drivers expect you to act like a pedestrian. This gives you a lot of leeway to find shortcuts without pissing anyone off.
I have a neon orange helmet and quite a bit of reflective stuff that's not too obvious in daylight. I have lights and fenders but only carry them in the wet dark season. I don't have a mirror but would get a Varia radar if I had more free cash. The "pros" might have more of this stuff than you realize, they like their bikes to be sleek and look expensive so a lot of it is small or built-in or more tastefully garish.
Trek Verve 1 is a good bike for commuting. It will mount up any accessories you like and keep working long term if you take care of it. There are a few iffy bits, but might not even crop up
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Genesis 49:16-17