Laugh - yes lots of questions.
Let's backup a step, and look at QoS, in general, which may address your questions.
Assume you have one interface with two active flows of traffic, say FTP and telnet. Also let's assume the FTP flow is saturating the link.
If the interface only has one FIFO queue, it's likely the FTP traffic will be adverse to the telnet traffic.
To try to minimize the impact of the FTP traffic against telnet traffic, we create a policy such as:
policy-map FTPnTelnet1
class FTP
bandwidth 99 percent
class telnet
bandwidth 1 percent
Would the above "help" the telnet traffic? It might, as we have two queues we can manage. If telnet needs less than 1 percent of the bandwidth, the above might be needed.
However, if we use a policy such as:
policy-map FTPnTelnet2
class FTP
bandwidth 1 percent
class telnet
bandwidth 99 percent
Telnet traffic is likely to be dequeued before FTP which likely means telnet won't be impacted by the FTP traffic. Yet, assuming telnet traffic uses very little bandwidth, the above policy barely impacts the FTP traffic. (BTW, the above is close to treating telnet as PQ would on most Cisco switches.)
Some important take aways from the above, having different queues allows us additional control over congestion issues; the reason FTP can be adverse to telnet, they are both using the same resource.
The above might be applied to a single interface, but what if we were using subinterfaces?
You might have a policy for each subinterface:
policy-map subint1
class FTP
bandwidth ?? percent
policy-map subint2
class telnet
bandwidth ?? percent
but how should the bandwidths be assigned?
Unfortunately, we have a real problem here. The two policies aren't managed as one. The FTP traffic can still saturate the physical interface, but regardless of how we assign bandwidths, each subinterface stands alone.
The above might be changed to:
policy-map subint1
class FTP
bandwidth 99 percent
class telnet
bandwidth 1 percent
policy-map subint2
class FTP
bandwidth 99 percent
class telnet
bandwidth 1 percent
Now, telnet will get priority within its own subinterface, but still telnet on subinterface 2 will not get priority over FTP on subinterface 1.
If we shape each subinterface QoS policy, such that all their aggregates don't exceed the physical interface's bandwidth, then the subinterface policies might be effective, but look again at the very first policy, where FTP had 99 percent. I.e. you can still have an issue.
The solution can be found by having QoS on both the physical and subinterfaces, but many Cisco platforms don't support this, or support it well.
I haven't worked multiple VRF as you propose, but I suspect, you're going to bump into similar issues.
