Electrical – How to connect a new smart switch to the wiring

The group of 3 white wires is your neutral bundle. Add the white wire from the new switch to it.

The group of two blacks is probably hot and a feed thru, connect both with the black from the switch.

Connect the remaining black (likely your load) to the blue wire.

Ground to ground. And I bet you have it in the back of the box. (The house looks new enough)

I'm going to disregard some of the questions about the existing switch because they aren't relevant except for purposes of learning, and I'm not sure I understand them clearly. You can simply remove that switch because you know the hot comes from the other switch, and the load is the remaining black which presumably leads to the fixture.

You're on the right track except that your assumptions in number 2 are incorrect. You would not remove any of those whites from the bundle. Doing so would probably leave you with an open circuit. You'll need to add a pigtail from that bundle to your switch, which requires a neutral, whereas the original switch did not.