So the thing about this is that there are a pretty wide range of system requirements based on your environment, how many solarwinds modules you are planning to run, and your tolerance for slow websites. Throwing it all on a single server with just NPM and NTA for 50 nodes is probably doable, but if it runs slowly then you basically get what you asked for by ignoring the recommended system specs and configuration.
In almost every case where I have seen a poorly performing SW install the database side of things was where they were underprovisioned or configured contrary to Microsoft's SQL best practices. Not doing standard maintenance and cleanup tasks within SQL, Raid 5 is garbage for IO, you really want to do 10, and you want to separate your data files, logs, and temps to different physical disks. And in the case of the NTA db that would also want to sit on a separate disk as well. So OS, Programs, SQL data, sql temp, sql logs, nta db. 6 partitions minimum, enough memory for the standalone app server, sql db, and nta db all added together, add up a similar volume of CPUs. At the end of that you still won't be able to get very much from support without being asked to split it all up and call back because your setup isn't compliant. If your org doesnt consider network monitoring to be critical enough to match the recommended specs then you are free to cowboy up and see how things turn out otherwise the path of least resistance is just to do what the admin guide suggests.
Loop1 Systems: SolarWinds Training and Professional Services