It depends :)

Financing:
When you're ready to start raising funds, C Corps (especially Delaware) are still preferred in the VC world although some angels are increasingly willing to invest in LLCs.

Risk:
When you're just starting off it's okay to have a holding LLC with DBAs. As you grow one or more of the ideas, you may want to separate out the risk so that if one company has issues it doesn't hurt the others. But it isn't necessary when you're early on. Once you add employees, cofounders, and/or investors, it's probably time. Your holding LLC could have equity in the idea and you could setup the idea as a C Corp. It's a good structure.

Also -- this ain't legal advice. Just general blahblahblah about legal structure.

Really good article from a fellow Seattle startup attorney here: http://www.startuplawblog.com/choice-of-entity/

This is a question I get frequently: Should I set up a new legal entity for each business I start.

When entrepreneurs are just starting or want to test a few ideas, they often group businesses under the same entity (or use a series LLC).

As soon as you can afford it (or if you have the money to start it correctly) you definitely want to have them each business in it's own legal entity.

This is primarily because of liability, financing and accounting reasons.

Liability
You want to maintain a proper corporate veil, distinct assets and liabilities.

Financing / M&A
Selling a company (moving assets, everything including domain, software, paypal, emails, etc.) is a mess if it is co-mingled with another business.

Accounting
Generally much easier if separate bank accounts, merchant accounts etc. This includes tax reasons but any sort of due diligence or audit will also be more difficult.

Partnership
Much easier to cut a deal with joint venture profit share or equity partnership if you can simply amend operating agreement or create a shareholders agreement and offer membership interest or shares to new person - without worrying about separating out other assets held by that same legal entity.

TL;DR : Generally better to have a separate and distinct legal entity for each business.

You could do a Series LLC which would allow you to set up multiple ventures while compartmentalizing the liability and risk.

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.

The best business structure for a tech company are as follows:
1. Sole Proprietorship: In this business structure, one person is the sole owner. With this business structure, it is advisable to hire a good accountant to figure out what the best way is for you to reduce your taxable income. This business structure is a good option for start-ups because it is easy and inexpensive to register and the sole owner has direct control of all decisions. In a partnership business structure, two or more people combine their financial resources to put into their business. A partnership is non-incorporated, and all partners share the profits the business earns.
2. Corporation: This business structure is formed at the federal or provincial/territorial level and is a legal entity that is separate from its shareholders. Shareholders are not responsible for the company’s debts or actions. Most start-ups are not at the phase where incorporation is appropriate. Incorporation is beneficial because it has limited liability, transferable ownership, and greater tax advantages.
3. Co-operative: This type of business structure can be for-profit or not-for-profit and is owned and controlled by an association of members. Co-operatives are the least common business structure, and it is often used to provide access to common needs. However, the decision-making process is long as it is democratic, and there is extensive record keeping involved in maintaining this kind of business structure. No matter what kind of business structure you choose for your start-up, it is important to consult with a legal professional or experienced mentor beforehand to make an informed and intelligent choice. It is useful to know your goals, business plan, and your vision for your company and lay that out for those who are giving you guidance in the structuring process in order to help them help you choose the best business structure for your start-up.
Besides if you do have any questions give me a call: https://clarity.fm/joy-brotonath