Most mods should be updatable, just be wary of major updates like BC6 to 7, and Mekanism 7 to 8 (definitely don't do this one, will break all the recipe changes to mek), and keep an eye out if they are updates to the newer forge versions without backwards compatibility (TiC is one example of this, IIRC 1.8.4 is the last version that works with the current forge version used by the pack).Thanks for the info
Is there a way for someone who didn't make the modpack to find out if a mod is update-able or not?
Mods I definitely encourage updating would be Mariculture and storage drawers, as they fix bugs, and you could update to the last BC6 version quite happily too.