IR based AC,TV and Ceiling fan controlling idea ?Harmony Hub

Hello Everyone, i wanted to automate my double story house with 3 rooms and lounge at ground floor and 3 rooms at 1st floor.
each room and lounge has 1 AC 2 ceiling fans and 1 TV .
i was considering Logitech Harmony Hub as solution .but i wanted to clear some confusions related to Harmony Hub .
Q1: First thing i am confused about is whether i can automate my Any IR based device with harmony Hub or there is any specific list of IR supporting devices? is Harmony a suitable device to control AC Fans or it is just limited to TV ?
Q2: i have found in several Q/As and Community that Harmony use activities to communicate with devices it means if i simply wanted to turn my AC on/off i have to set 2 separate activities for ON and OFF ?? can i simply turn on/off device without Activity ? and i am running one activity will this halt all other activities ? can i run two activities concurrently ?

if i am using Harmony Hub and wanted to automate my All AC fans and TV, i would be purchasing different harmony Hub for each room . so total i will go purchase around 7 Hubs each for different room . so is it Ok and can i connect 7 Harmony Hubs with Single router on single Account ?? What is maximum limit ?