mongodb atlas use secondaries to reduce cpu usage

I have M80 atlas cluster(128GB RAM and 32vCPUs) with 3 replicasets. most of the time my system use around 10% of RAM and 10% of CPU, during high load CPU spikes more than 100% leading to autoscaling of cluster evthough i have all the required indexes(I added them based on atlas performance advisor). I’m trying to cut the cost, i noticed only primary's CPU is shooting up, so if i start reading from secondaries, can I reduce the CPU usage or 32 vCPUs are actually shared across 3 replicas and I wont see much diffrence? as per my understandin it would not make a different if writes are causing CPU spikes, but i see a correlation between CPU usage and read operations.