Beeswax DSP (owned by Comscore) is a popular alternative in the programmatic ecosystem to many you already have connections for. They have an API with all of the info you’d need and have one of the best bidders on the market for those focused on QPS. Many ad agencies using Beeswax would use Windsor, off the shelf options are very limited in comparison to those similar such as StackAdapt, Simpli.fi, AdForm, etc.