Why is query processing faster in local mongodb than in replicated one?

Question

MongoDB

There is a combat base (BB) in replicas (Master, Slave, Hidden + Arbiter) and a local base (LB) for development (copy with hidden replicas).
With the same requests in LB and BB, the first one shows the result almost 100 times faster, despite the fact that the BB is on a powerful server, and the LB is on a regular PC.
1. Could this be due to the fact that the BB is in a replica and one of the replicas (hidden), which has a narrow Internet channel of 2Mbps, slows down the primary node?
2. When I merge a backup from a replica (hidden), the dump time takes 24 hours, if this replica is stopped and started without a replica set, then the database is merged in 5 hours. What could be the reason?
PS The engine on LB and BB is wiredTiger, on hidden is standard MMAP. All bases of version 3.0.6 except hidden - 3.0.4.
PSS As far as I know, the replica does not care what engine is running on the node and the version does not matter.