If the Google app is pre-installed on the phone then you won't be able to replace it (at least not without root). And "running alongside" means adding a new app, which will store its own data, in addition, so if your problem is storage surely that would make things worse?
I don't really know about the Google Go app, because I don't use the Google app itself (I can do search with a web browser, dislike search widgets as clutter on my desktop, don't use Assistant or Google Home, don't do voice search, so all-in-all I really have no need for it). But this raises 2 questions: what do you use the Google app for, and can Google Go replace it for the things you do? If the answer is that having Go would make Google redundant for you then you can probably save a bit of space by clearing data for the Google app and disabling it, but do make sure you really don't need it (i.e. you aren't using something that relies on it without realising).
But it also sounds like your problem is storage space (to me "memory" means RAM, which is different), in which case why do you think that the Google app is the cause? Storage filling is the net result of everything on your phone, including all of your other apps, whatever media you store in the internal storage, etc. So the starting point is to work out what's actually using the space. Remember that app caches can be cleared with no loss (app data is different: don't clear stuff unless you know you don't need it), and you'd be surprised how big caches can grow for things like browsers or social media apps. Clearing caches is only a temporary fix (they fill up again), but if you need space for something specific then that might suffice. If you have persistent problems the only real solution is to remove things that you don't really need.