Hi Arkenor!
No, everything within the submod essentially changes the recipes for uplifting planets. Instead of using Minerals, you'll use Planetary Mass instead. If you run the game without this mod but with Gigastructures enabled, you'll only be spending minerals like in the main mod.
Nothing bad should happen as far as I know, so you should be all good.

Though, even though I haven't been able to update the mod to the current game version, nothing has changed to the mod since it's last update. Theoretically it should still work normally.

I see this isn't currently working? Will anything awful happen if I use Gigastructurs and Celestial Engineering together without this submod?

WARNING
I'm experiencing some issues trying to update this mod I'm not sure what the crack is, as it is trying to pull information from the mod, in a place that doesn't exist. There will be a delay for now, however the mod should still work normally.

Hey Paladin One
I appreciate that you've created a submod of my submod. There are aspects to my submod that still require some attention including what is underlined in your submod. I think we definitely should have a decent chat about what could be done to enhance the mod and/or fix these issues. At this moment I'm unable to work on them due to real life taking priority, however when I do get back to work, I can ping you a message.

Let me know of a way for us to work when ready

Heya
So I'm also playing with both Celestial Expansion and Gigastructures, and I noticed two subtle compatibility issues between CE and Gigas:
(1) Gigastructures reworks how Habitats pick up resources from the planets they're built around, and it makes Habitats inherit SR deposits from planets. However, it doesn't inherit from CE's Underground deposits.
(2) Frameworld Outposts can produce resources from planets, but they also don't inherit from CE's Underground deposits.

So I wrote my own small (unlisted) add-on compatch mod for these two functions. If you'd like to use any of my work, or discuss other ways of resolving these issues, I'm open to talking with you.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2811583149

Also, as I ran my trial runs for updating the mod to 3.4, I note that a change with PM costs will take place. PE1 takes us all the way to Very Small planets right away. In the interest of cost effectiveness I think I will when I make the next update, make it so that all costs from and above Small will start to cost Planetary Mass. I know it'll be limiting until unlocking PM from GE, and I am considering the option to bump up to Average or Large, however I don't want to make it too easy to farm the matter.
Though now that i consider it, could you guys imagine a galaxy of only size 75 planets? might be slightly OP but that would still take a long time even with the limited generation from my mod

Update uploaded!
As far as I could tell, there were no issues with compatibility with this mod and GE. If there are any issues as a result of the game update, this mod or GE, please let me know so I can fix it right away.
Thanks for playing with CE+GE!

yeah i just think there should be some cheaper cost for small expansions but PM is needed for anything above planetary expansion 3 tech

Hello DecentNameHere
Thank you for your comment and suggestion :)
I like the idea of cutting the cost of PM from lower level decisions, however if I remove/replace the costs from everything before Planetary Expansion 3, it'll make it a lot easier to farm for PM. Especially considering when it comes to removing mass from planets via the Gigastructures way, it'll remove the mass all the way to size 1 or Small Asteroid-scale.
I could, in theory, implement it so the PM costs start as early as Small or Average planets while minerals are the general requirement from everything at and before (Very) Small, giving some room for PM farming but at the same time, I'm not sure how I feel about it*. I don't want to make it easy or too hard to generate the mass
* - If anyone else think this is an excellent or is a preferred idea, please let me know and I'll make a change as soon as I can.

thanks for the compatibility mod, i think it would probably be a good idea to remove the planetary mass cost ,at least at early level (e.g before planetary expansion 3) as mass is locked behind 3 other ascenscion perks and takes very long to unlock while i could very supply minerals to it.

You're very welcome!

Thanks for the the compatibility sub mod :)