1. If in our new building we will do CAT5 instead of CAT6 are we able to still get the same speeds (as those of CAT6) for end users that are connecting to the LAN with CAT5 but with switches that support Multigigabit? Or is it something that only works when having Wave 2 access points?
First of all, CAT5 isn't sufficient for multigigabit (NBase-T) in the first place. You need a minimum of CAT5e. The most common application for NBase-T is in supporting 802.11ac Wave 2 APs, but as long as the end users are using NBase-T NICs, they will get the speed benefit as well.
2. Do you think that cables are still needed if you have 802.11ac Wave 2 access points? What are the advantages of having both wired and wireless infrastructure apart from redundancy? Would you go for both?
It depends on your requirements. A wired connection is always going to be faster, more secure, and more reliable than a wireless connection. This is because a wired connection will almost always have dedicated bandwidth over a closed physical channel with end-to-end management. Wireless connections share the connection with other subscribers to the AP and transmit over the air. Ultimately, wireless is about convenience more than anything else. That said, for most people, shared wireless connections and over the air encryption are good enough. It depends on your business requirements.
