I've been using UW for a few years. It is very useful but you have to be careful. Lot of unreliable people out there. Over the years, I've narrowed a couple of people I keep using. And have excluded others. Few things:
1- It's best to give clear instruction. I tend to build GSheet on what I need, interact a lot of Skype at the beginning
2- If you are searching for mails, do use email verification services. I find that people I work with tend to have a 95% success rate but, at the start, best to be on the safe side rather than burn your mail server (bounce rate need to be low)
3- Focus helps but if you are testing things out, you could use a platform like Reply.io to test out a few verticals and see what works or what doesn't work.
4- It feels your target markets are a bit too generic. Using UW, you'd have too wide a net. There are various ways to narrowing things down, from geos to title to company size or even keyword in company profile. Again, what is possible is to set a filter and share it with UW.

Hope it helps, UW etc... are useful and best in my experience than the products out there. But it is a bit of work (no pain no gain). Happy to set up a call if you see value (am rather new to Clarity so not too sure how it works!). Best, H