Some questions on Cisco QoS queues vs buffers and general help

So I’m a little confused about one of the knobs on Cisco QoS (ios-xe on 3850/3650) that is queue-buffer ratio.

So look at this policy map below

policy-map Outbound class VOIP priority percent 5 class VIDEO bandwidth remaining percent 15 class ASSURED bandwidth remaining percent 20 class class-default bandwidth remaining percent 60 

So the way I understand it this configuration breaks the interface up into four outbound queues. One of them is a low latency/strict queue for class VOIP and guaranteed it 5% of the bandwidth. Next queue is for class VIDEO and guarantees 15% of the bandwidth. Next is the 3rd queue for class ASSURED, and it’s guarenteed 20% of the bandwidth. The 4th and final queue is best effort and it gets a guaranteed 60% of the bandwidth.

Each queue can go above their guaranteed limit, so long as the interface isn’t congested... except for the priority queue which will never be allowed more than 5% of the interface bandwidth? (Is this actually true?)

But that just has to do with bandwidth, or transmit rate? But since no buffer ratios configured, all the queues will split the interface buffer space so they’ll each get 25% of the interface buffer?

So as traffic is switched every bit will transmit as it arrives. This goes until the interface is filled up I.e. until it can’t transmit any faster. So once that happens, additional traffic that needs to be sent waits in line in a buffer.

I guess I’m just a little confused how a class of traffic can be guaranteed 15% of the bandwidth but it holds 25% of the buffer space. Maybe I’m not thinking about it correctly. I think an animation would probably help me, but can’t realky find anything out there.

So when would you adjust buffer-ratios?

Does the policy map above make sense where you think it’s a sane configuration. Would you want to give voice/video more buffer space because they’re more sensitive for user experience, or would you give them smaller buffer since they shouldn’t be waiting in line as much.