The original 1995 Neon Genesis Evangelion TV series was anime original, with the manga being released at a later time. It was essentially just a manga retelling of the anime TV series.
There wasn’t a ton of fanservice in this manga, mostly just weird nudity. For a much more enjoyable fanservice experience there was the ecchi manga spinoff Shinseiki Evangelion Ikari Shinji Ikusei Keikaku. Though of course, that version is hardly canon.
Shinseiki Evangelion (complete)