what upgrades ?

The only two that - I personally would make, before I even plugged an ender 3 in.
Would be adding a second z axis motor and screw thread, you can get it as a kit.
And moving the extruder to the top of the hotend, tomake it a direct drive printer.
You need to do the z axis first.

Once you've done those two, you're 2/3rds of the way towards a proper prusa design i3.
Adding linear bearing guides for the printbed is probably too difficult, it is what it is.

And if you do those two things it means that you can then print at speeds of up to 200mm/s. With no other changes.
Although generally speaking 150mm/s would probably be the sensible max.

Without both those mods you're stuck with creality's shitty design and speed restraints - no matter what else you do.

personally I'd stick to a 0.25mm nozzle.
I know it doesn't sound like much difference. But I have used a 0.25mm nozzle. And you don't need to make a lot of changes from 0.4.
Temps up slightly, retractions shorter and speeds only a little slower and the detail level is pretty damn impressive.

With a small nozzle and stock ender speeds - yeah 10 days is about right lol.
With the two mods I mentioned, you can probably cut that down to 2-3 days :-)

I don't use cura and am not a fan of pre-made profiles anyway.

Prusaslicer is way better than cura and easier to use (not hard).

In the long run it is always much better to learn what different changes to slicing settings do and just make your own profiles.
Every setup is slightly different. So what works for someone else might not work for you.
You're undertaking a fairly impressive and long running project. So in the long run actually learning how to get the best from the printer can only help you :-)

Thought patreon was for giving more money to rich people on youtube ?