I see this from time to time, and it's getting more frequent on the forum and fb, basically everywhere.
Here's a few simple steps to determine how many accounts it can run on your particular machine. This is more catered to amazon vps because many people are struggling to understand why it cannot handle relatively small sets of accounts.
1 Use http://quickurlopener.com/ and open up as many social pages as you can
2 Use this https://technet.microsoft.com/en-us/sysinternals/processexplorer.aspx and check for bottlenecks
MP itself uses around 250MB for my setup, without running any actions. And it uses multiple browser process instead of lumping it into one. This means, if you're able to open 50 to 100 IG profile tabs while maxing out your ram, you will most likely need to divide it by 2 (rough figure). So for the amazon vps, if your setting is using less simultaneous connection, you can cramp lots more accs. If you have it run 50 simul accs, then you will imagine how many browser process it opens.
The key point being, how many simultaneous actions can each account run at any point in time? You can even load 100 accounts in there if they do close to nothing. Just like if you open 100 tabs in your browser and they all perform those action at the same time.
Once it crosses the ram limitation, you will see lots of disk activity. On amazon vps, since the ram is limited, the rest of the process will be using the disk. This is called swapping. You will experience this alot on a fairly old laptop.
For the record, an amazon vps is not much different than an old laptop. If you find it really slow and painful to use an old laptop for relatively light browsing usage, imagine what happens when you try to open 20 tabs? Then imagine again, what happens when MP is doing alot more things than a human with super duper multitasking skills?
Addition. I haven't touched on the CPU, and here I shall give my point of view why the CPU spec matters as well. It is hard to measure how much the CPU is going to affect the operation on a VPS, so i compared it to a PC that I have running pentium G620.
Here's the general spec
2 cores 2.6 GHZ (no HT)
Now this you would think is going to be pretty fast, but actually, it's not. The day to day browsing of 20 tabs is slow. The only thing that changed the speed a little is when I added the SSD. But the main bottleneck here is the older generation Pentium CPU.
Translate that into amazon vps, it only has 1 core (and you're not exactly getting that 1 core, but rather a thread), and for optimum performance, a browser uses as many cores as it has. And it's also not all about the cores, but rather the generation of CPU it uses.
TLDR ; Perform a general day to day browsing on the machine you intend to be using for MP, and get a general feel of it's speed, and you will know it's potential.