I'm sorry but I would leave the concrete as-is or have it polished up and then leave it.

The garage conversion was messed up by the prior owner which means the proper tie-ins from slab to walls (at the point of changing direction ie. horizontal to vertical surface) wasn't done to "living standards".

Sadly, most people do not realize that a garage is built to different codes than the house. Garages are not considered "living spaces" and are therefore not subject to the same rigorous codes required inside a home. Things like moisture mitigation, insulation, venting, etc. are well below the requirements for a house.

Because the original project was mucked up, I would recommend you work with the concrete and then leave it alone. Once the "ugly" has been taken out of it (or off of it), you can then have lots of fun working with large indoor-outdoor area rugs. Yah. The stuff you can put on your deck.

You are welcome to work with decent looking indoor-outdoor carpet if you wish to have a "real floor". But the concerns I have with that are many. You can't remove them easily. They are hard to "clean up" if they get wet/musty, and they are more expensive than out-door area rugs.

Until the conversion is re-done (probably not worth the $$$$) I would not put too much money into the flooring.

Epoxy floor finish for concrete floors.

In other threads, I have read and learned that finishes on top of concrete floors are hella difficult to remove, in the event you ever decide to change that flooring. There was a recent thread about this--can't find it now. Of course, your choices certainly depend on a lot of factors (local real estate market, value of your house, family dynamics, your taste). In your shoes though, I would investigate Luxury Vinyl Plank, especially the "waterproof" versions, such as Coretec, to name one brand, and I'm sure there are others. I just think it will look nicer, and feel nicer on your feet.

There are specialty tools design for coating removal and concrete prep. Installers that restores concrete slabs should have these tools in their artillery.