Lightmaps Performance/Quality balance

Hi everybody. I am moving my first steps in Unreal so please forgive me if the answer to this question might sound obvious to you. You know, i am an old-fashoned static CG illustrator :wink:

Here’s the story. I am porting to UE an archeological reconstruction while trying to keep everything well organized and optimized, either for performance/quality reasons and for learning better.
In the pics you see the floor of an underground church, that will be quite poorly lit with just a few sconces and natural light that will come only from the entrance and from a zenital oculus in the terminal part.

Eventually, the question. In such situations would it be more effective having a unique object with a unique Lightmap for the floor, or to split the floor in tiles such as the one shown in the image?
I am testing performance anyway, but i would love you all if you could provide also a feedback based on your experience. Thanks in advance