I help run qualitative and quantitative experiments for early-stage B2B SaaS companies to help inform their go-to-market and launch strategies and tactics with data, for both new and existing products and features. (This goes well beyond A/B and multivariate testing.) I especially help with value proposition design and language-market fit. I build, grow, and engage communities. I work from the perspective of Customer Success or CX-led growth to help create WoM, brand advocacy, network effects. I don't do paid marketing or advertising. I do things that don't scale. I help create genuine relationships. I won't help you with short-term "wins." I don't do aggressive "growth hacking" type things. I play the long game. Top 15 hunter at Product Hunt, Mentor at Growth Mentor, Moderator at GrowthHackers.com, in The Shine Crew, etc.
Because you are still in the idea stage, the first thing you'll want to do is ensure that you have product/service-solution fit. You need to validate that your service solves a real problem and that there's a big enough market to develop a successful business around it.
I recommend conducting research on achieving product/service-market fit, and actually establishing it before focusing on marketing tactics.
When active users have opted-in to receive e-mail communication, e-mail marketing is an extremely effective channel for customer retention.
It isn't as effective for user growth via purchased e-mail lists because recipients are not users yet and may not have opted-in - they haven't developed a relationship with your business, so when they receive e-mails, they aren't recognizing them as coming from a trusted source.
Every business should be utilizing e-mail marketing and marketing automation to communicate with their users / customers and improve retention.
Without having all of the details concerning your app:
You shouldn't have any issues with launching the consumer-paid product, however if those same consumers will be the end-users for the product you're developing for enterprise clients, there could be some conflicts of interest.
If there aren't any conflicts, you'd still want to structure your business model to address these two markets separately.
Each buyer will have very unique pain points, decision processes, price tolerance, and support needs.