Suggestions? At a minimum, for a Single Session VDI, use 4vCPUs and 8 GB of RAM. This specification is for your average (non-power) user. If you are an Azure VDI user, then I would suggest the Burstable VM B4MS. It is cheaper than your other options and still gives the user the power they need to do their work.
What about multiple session VMs like Azure Virtual Desktop/Citrix/Horizon? You want to ensure each user logged in has at least 1.5 to 2 vCPUs. So on a 10 vCPU box, you are looking at about 6 users per box if you are virtualizing for the experience. Your users will complain a lot less if they have the CPU power to do their work.
Most customers will believe they need more RAM as a resource. Sometimes that is true, but oftentimes the user experience is improved by vCPU adjustments. Trust me, you will thank me later!!
By the way, you will likely never see the spikes or the issues by using monitoring tools outside of the VM so don't try that.