As you are mentioning the business coach I assume you wish to travel in 1st class.
As a general saying, there is no need to reserve seats on IC trains, unless you wish to travel on the Zurich to Bern route (or v.v.) during rush hours, or you are a party of multiple people. There are usually enough seats available in 1st class.
You cannot choose the exact seat; while making a seat reservation, the system will simply allocate you a seat according to your given seat preference.
The business compartment is destined for business people, calls and talks are allowed provided the conversations are conducted at a reasonable volume and do not disturb fellow passengers.
Btw, we do have an English-speaking SBB community, too: SBB (EN) - SBB CFF FFS Community