Elastic stack upgrade to 7.1 or 7.2

I need some inputs on upgrading ES stack specifically with my project and let me know if you can help anyways

we have search platform ( Elastic search and Kibana) on 6.1.3 version . WE have around 125 million documents and few other indices on ES . We intend to upgrade to latest 7.x version in coming months . We want to know what is the best path to upgrade to 7.1 or 7.2 from 6.1.3 without encountering any issues due to upgrade?

The video ( https://www.elastic.co/webinars/upgrading-your-elastic-stack) talks about upgrade path for 6.7 as either
a) 6.7 -> 6.8 -> 7.1 or
b) 6.7 ->7.0->7.1

Does it mean upgrade from version 6.7 or below (6.1.3 in our case) to 7.1 or 7.2 is not recommended ?

Kindly provide the inputs on best practices and also possible issues (if any) we may encounter during direct upgrade from 6.1.3 to 7.1 or 7.2 .