Yes, it seem very sensible and should be very safe.
But that doesn't mean you won't encounter any phone verifications. I have experienced that with good 1+year aged accounts, quality proxies and a decent warm up, there is still a slight change for your account to prompt a PV when adding the link or using high settings. It's very unlikely that you'll never have to deal with them, but with your strategie it shouldn't be much.
Did you check if your VPS was really laggy? With that I mean if your RAM and CPU usage was really too high, or just if it seemed to be laggy. I, for example, was also shocked when first logging into my vps that everything seemed laggy, but that's just a sideeffect of logging into it via remote desktop control. My ram and cpu usage was only 20%.
Furthermore, nobody can really tell you how many accounts you'll be able to run with your laptop as we don't know your specs, but with a decent laptop of 8 GB ram those 50 accounts shouldn't be a problem.