Frankly if you don't have proof of concept you should incubate them all under the same legal entity. As you start to generate profit, raise money, etc. then you can look at creating a legal entity but the only people who benefit from the attitude that starting a company starts with forming a legal entity are the lawyers and accounts who get more work from the process. I've owned and operated 13 businesses in my day and had all kinds of other ideas I played with. So often I'd have an idea sitting maybe I'd have some meetings about it etc. but it would never go anywhere or would get pushed to the back. If I'd formed a company for each of these I would have wasted a ton of time and money. Start with market validation and get some customers first then create legal entities as they become something real.