1. The number of VMs inside a resource pool does not affect any other pools or virtual machines outside this pool. 10000 shares are 10000 shares, no matter how much vms are inside that pool.
2. If you do not change anything your vm has automatically 1000 shares per CPU. To answer the question you have to know how the number of vcpus from the vms outside the pool.
Example, assuming they have 1vCPU:
pool 1: 10.000 shares
pool 2: 10.000 shares
vm 1: 1000 shares
vm 2: 1000 shares
That is: 22.000 shares total
makes about 4-5% for both vms.
PS: Check the "Resource Allocation" tab from your Cluster and it will tell you exact what you have asked.
