Virtual Machine manager is too slow

[Simon95]

Goodmorning everyone.
I am making an Xpenology device with this features:
- Jun's Loader v1.03b loader DS3617xs
- DSM version 6.2
- Motherboard: AsRock Q1900M
- Processor: Intel Quad-Core J1900 (2 GHz)
- RAM: 8Gb
- Hard Disc: 2X SeaGate IronWolf 4Tb (each)

I have an old PC based on intel core 2 duo and 4gb of ram with Windows 10 running a management software. I created an image of this PC and poured it into an instance of Synology Virtual Machine Manager with this specs attributed:
- 4 CPUs
- 4Gb RAM

- 100Gb Space
To my surprise, I found that the operation was successful and the system transferred to Vm works perfectly and the clients pc connect to the management system without problems. The only problem I noticed is that the management software is much slower. Example: From a client PC, to open the supplier list, the time taken before (old "server" pc) was about 0.5s, now it takes 1.5s. It is not a disproportionate time, but the difference is felt and it is annoying.
What is the cause of this problem? Virtual Machine Manager Limit? Disc speed limit? (the new ironwolf and the WD red on the old "server" pc are all at 5.400rpm, so I don't think that's that)
CPU J1900 limit too low? (as I believe it is)
If I replace the motherboard and CPU with something more performing (GIGABYTE GA-H81M-DS2 + Core i7-4790K for example), could the performance of the virtualized instance increase?
Thanks a lot to everyone for your advice