How to choose: answering the main questions
One server or several for an ERP system?
For up to 100–150 users, an 'application + DBMS' bundle can run on a single dual-processor platform using separate VMs. Beyond that, the DBMS should be moved to dedicated hardware with NVMe — this way, scaling does not require migrating the entire system.
What is critical for ERP speed?
DBMS disk subsystem (NVMe in RAID10) and core frequency. Users feel transaction latency, not the megahertz on the spec sheet: look at database response times under load.
How to calculate resources?
Vendors provide standards per user (1C: ~1.5 GB RAM and 0.1 core per active user). Take the peak estimate × 1.3 for a safety margin — and consider memory expansion slots.