Doubt anyone will see this, but is it worth reading the manga when you have just watched all of the anime? Or are they mostly similar?

just my personal opinion. novel > manga > anime and almost never any other way.

im somebody who first started reading a manga then watched the anime of that manga and was disgusted. in the years to follow, anime has only served to disappoint when compared to its source material. it's better to not compare them at all. if you enjoy anime, you should do exactly that. but if it leaves you feeling unsatisfied (as oftentimes it will) i suggest dumping it entirely for the manga.

and if you are REALLY into a story, you might very well turn into a novel reader. at least this is my experience.

to each their own 😜

Anime usually only use a small portion of the manga source material. If you're already a fan after watching; getting more quantity (even when it could be lower quality) will be greatly rewarding

this hard rule might not apply when music is concerned

you could have a middling sci-fi series but suddenly it's a top 10 all time because fans love the music so much

To actually answer your question:

I don't remember there being any difference between the anime and manga besides the fact that the manga takes place in the 80s whereas the anime is in the 2010s.

That said, a quick look online tells me there are a few small differences. Some smalls scenes got left out of the anime, and Kana's relationship to Shinichi was built up more naturally (i.e. gradually) in the manga.

Given the similarities, I'd say it's only worth reading if you're particularly interested in the story, and don't mind retreading lots of the same content.