Each work place and job role have their own rules around your questions.
I started a job 2 weeks ago working solely from home. In the 1st meeting with my boss, she explained that she was flexible with start-finish times. For example, if I want to go to lunch for 2hrs or the bank/shopping etc in the day, I can start earlier or finish later. This obviously doesn't work in all roles. Most other companies I've worked from have core hours, so you need to start between 8-10 for example. Other have stricter start/finish times.
I would think that their IT can certainly track your logged in hours, along with website you search. They wouldn't know if you are sitting watching TV though. I have re-set my screens sleep time to longer, because if I need the loo, or to get a drink, I don't want the screen the sleep and look like I'm not there.
I used to manage staff and recall IT had to check log in for staff in another team. It was very crude data though. After investigations, it showed that if someone logged in say facebook/youtube etc once in the morning and sat on it all day, it only logged it as 1 log in. Whereas someone doing work, who then logged into other sites, closed them, logged in again showed multiple log ins within the 1 day.
I personally only do work related google searches on my work laptop, and keep personal things on my own laptop.
My current team is fairly small- ranging from 3-6 working each day. Generally (depends who is working) someone will group chat on skype to say hello in the mornings, and say who is working.
In the afternoons, some say goodbye, others don't.
My team are friendly, and happy to help or do chats, but also majority have 20+ yrs in our profession- only WFH this past year or so, therefore mainly hands on experience beforehand.
If WFH was my 1st job, it would be different though and possibly more difficult. Although, if I was younger, and it was my 1st job, I would likely be FAR more proficient in teams, skype, excel and computers in general!