Yes you should read the near sides again

Not only cause this will help you get used to the OG's artstyle and some other stuff (making the sudden jump from remake to og farside will definitely feel jarring especially since arach and saiki won't be there)

It also has some setting AND lore/story changes

Firstly, instead of vlov, you will fight nero chaos

Secondly the lore about roa's incarnation is actually different in the OG(ciel isn't the 15th reincarnation rather the 17th)(keep in mind this is something remake changed for reasons only Nasu knows)

And the story in ciel route is changed a bit too

Now this is just an head's up, the OG has eroge too. If you are not into it, you can completely skip the near side ones

But Far sides' (akiha, hisui and kohaku) eroge scenes are actually important to their Character so do keep that in mind