AdvancedHMI does not pose any limits on the number of DataSubscribers or the number of tags per DataSubscriber. The limitation comes from the bottleneck of your hardware and communication link. The PollRateOverride is the target rate for round trip time of updating all subscriptions. But if the communication link does not allow that rate then it will update as fast as it can.
For instance, if you are trying to upate 7000 tags that are consectutive and the driver reads them in groups of 20. that means it will take 350 reads to complete the round trip. Now let's say you are using Ethernet and the round trip per read is 15ms. The absolute fastest update is going to be 5.25 seconds. Even if you put 1000ms for PollRateOverride, it will still only be able to do it in 5.25s.
