You might consider a multisite wp install and manage updates with a plugin like Broadcast. Not sure if their free version or the Pro enables the overwriting of existing content with mother blog post updating, so it can easily get distributed to all network blogs. And of course, you can this way map each network sub to client domain or subdomain.
Elementor Pro enables custom parameters so you can send to the same lander but have certain text on it dynamically change depending on the link visitors get.
Unless you’re testing CRO for domain names or to make it look like it’s different domain sources for the campaigns. Useful for SEO and if you run ads or other types of marketing with high burn rates where multiple domains need to be deployed.
With FunnelFlux you will have drag and drop funnels supporting all types of traffic [email/PPC/search, etc], rich tracking, conditional redirects, split testing and more and custom CNAME domains supported while you track what’s going on.
If it’s whitehat landers you give your affiliates AffiliateWP plugin might be a good solution in addition to Elementor Pro.
Another alternative – Static HTML landers.
If you need a good fast EASY drag and drop HTML builder check out the PixFort bootstrap HTML builder – hosted online and works best from a windows machine [not mac or win on mac]. Can even do pops with multi-steps and has a lot of nice drag and drop elements plus can edit HTML code when needed. I made a great lander for FB ad campaign and had an 80% CR optin on it.
Use CF [cloudflare] free account; setup DNS, tweak settings and set a few free rules alongside free SSL cert [or flexible SSL].
For the static lander – add .htaccess with caching optimizations in there for max effect and page load speeds.
PixFort and also other builders like Weber or Gum are found on ThemeForest.net Can place the HTML pages on S3 buckets, various free hosting yada yada.