"Note: Nightow changed publishers to Shonen Gahosha and the series continued to be serialized in Young King Ours magazine. Due to the original publisher retaining the name Trigun, Nightow had to change the title to Trigun Maximum, which isn't a sequel but a new name for the rest of the series. The first 3 volumes were published under the title 'Trigun' and the entire series compiled into 14 books as 'Trigun Maximum' (the numbering was also restarted when the title changed)." Anime: https://kissanime.ru/Anime/Trigun-Sub Side Story: Trigun - Multiple Bullets
The original was so chaotic and fast-paced. I think it's better to watch the anime first and then read the manga to understand what is going on better.