You're comparing a Tube site with a membership site. Both of them use a CMS, but they're a little different but also very similar with features and options. If the client's budget is tight, we recommend pre-made templates; then we explaining to them that there's only so much we can do to chance the design of a template.
For a custom design, we create the website using Photoshop. Once the client approves the design and it's perfect for them, we move to coding the site in responsive HTML so it's flawless on any device it's viewed on. At this point, we verify that there are zero errors and move on to the CMS stage. We work hand and hand with
Mechbunny for most of our custom and out of the box solutions. Most of our clients want a custom design so it's not very offend we use pre-made templates and we've never used a site builder for adult sites.