Hello and welcome!
The answers you are looking for are going to depend on the product type and chipset. For example, PMP450m (medusa) MU-MIMO and beamforming works differently than Wi-Fi. However, since MU-MIMO and beamforming are most common in 802.11 products (and since you are asking about the E410), the information below will apply to all of the E-Series 802.11acWave2 devices (E410, 600, 430, 700).
Good info on the technology in general is available on our Cambium College: http://community.cambiumnetworks.com/t5/Connecting-U/Cambium-College/m-p/69663#U69663
At a high level, MU-MIMO and beamforming only work on 802.11acWave2 chipsets (MU-MIMO in particular), and 802.11acWave2 only works in 5GHz. Therefore, with dual-band radios, the 2.4GHz radio will max out at 802.11n technology (802.11b/g/n), but the 5GHz radio will max out at 802.11ac (802.11a/n/ac).
MU-MIMO is a chipset based technology, meaning that for MU-MIMO to even occur, both the AP and wireless client need to have 802.11acWave2 chipsets within them. In that scenario, MU-MIMO works in the downlink only (AP to wireless client), and your mileage will vary in how well it actually performs in the real world. Most likely, you will see the most benefit from static devices (i.e. smartTV's), but there are a host of variables that will affect its operation.
This link goes into more detail and I've attached a presentation that I've used in the past for general Wi-Fi technology principles (target audience is Telco's, WISPs, MSP's and is not Cambium specific). It is getting a bit dated, but the principles remain the same. https://community.cambiumnetworks.com/t5/cnPilot-E-Series-Enterprise-APs/Beamflex-Ruckus-equivalent/td-p/104729
- Cambium-cnPilot-WiFi-4-2017.pdf (1.54 MB)