As for URL structure keeping it shorter is better. Please do read this blog as well. https://moz.com/blog/15-seo-best-practices-for-structuring-urls
For ranks and quality backlinks, it's not the number of different platforms you use, but the how effectively you are using each platform that will make all the difference.
Try engaging your target customers in real time discussion on chat on the website and also on blogs/forums. It will help you a lot to get traffic and branding.
I focus on very few platforms for my clients and some results are attached om this quora answer Travel Website results