Thank you for your post and welcome to the Bose Community.
The Soundbar 700 is part of your Smart Speaker range. There are no limits to how many Smart Speakers you can connect, however, a limitation may be your network bandwidth. The more speakers that are connected through Wi-Fi, the more likely you are to encounter streaming problems. Regarding the accessories for the Soundbar 700, you can have a set of 2 surround speakers and 2 Bass Modules if you wish. Please note that the Bass Module must be the same variant. For example, 2 x Bass Module 700 and not 1 x Bass Module 500 + 1 x Bass Module 700.
I hope this makes sense and if you have any questions, please do not hesitate to reach back to me.