Simple Queues very reduces throughput.
When rules in Simple Queues no - RB750 has a WAN->LAN - 100 Mbit/s. CPU-30-40%

If I add at least one rule Simple Queues, the maximum speed WAN->LAN is reduced to 45-50 Mbit/s. CPU - 100%.
Also it is established in Simple Queues MAx Limit Upload/Download = 100Mbit/s.
Although the Simple Queues rule set not even for my local IP-address.
Why?

Tested on speedtest.net

I use Dynamic IP. fiber.

Your device is way too slow to handle that speed with simple queues, you could try queue tree but I doubt that it will help that much...

I'll try queue tree. but I doubt...
Here I think the problem is inefficient algorithm Simple Queues.