That sounds like a pretty good plan. If you do a clean install from the recovery partition youll either get Lion or Snow Leopard in which either one would be sufficient as well as small.
If it currently has High Sierra installed you would have likely gotten an EFI update which allows for internet recovery and it may force you into high sierra as well, but it really doesn't matter which you use aside from space. You can also disconnect the ethernet cord and it -should- boot from the recovery partition instead giving you an older version of OSX.