I think it's important to get terminology correct. AOI Parameters can't be grouped into a single read due to the two EnableIn and EnableOut parameters which cannot be set to at least readOnly external access. However, AOI Local tags are perfectly fine to read and can be read efficiently.
UDT type members similarly can also be read efficiently.
I found no significant difference between reading UDT members, members of aliased UDTs, members of UDTs within arrays, or nested UDTs' members.
I noticed a very slight degredation in read speed of AOI Local tags, whether they were UDT types or basic types, but I would consider it negligible.
Reading AOI Parameters have significant impacts to PLC response time. On an L82 it was approximately 10x the response time compared to the other tests.
Note: all of these results were performed where every tag/member/parameter in the structures read was set to at least readOnly external access. Setting just one to None destroyed performance to approximately AOI Parameter read levels, regardless if the item is read by SCADA or not