In THEORY, MCPS differentiates within a class so that the teacher meets each child at their level, whether they're significantly below grade level, significantly above, or somewhere in between. In reality, struggling students might get extra help, but above-grade level students often get little or nothing at their level.
I suggest you contact the school directly and ask what opportunities would be available if the school determines your child is at an advanced level. Be aware that elementary schools in MCPS have a high level of Principal turnover. A new principal can change everything.
You might consider an immersion program. Learning a new language can provide a challenge even if the subject material is already mastered. That's the route we took for our kids who were advanced. It worked well in early grades, but by third grade, however, the foreign language skills were sufficiently developed that it didn't compensate for the weakness of the curriculum. The school's basic stance was that we should be grateful for the immersion and expecting anything extra was unreasonable. "Differentiation" per MCPS policy was theoretically practiced, but was up to teacher implementation. My two kids in the same school had vastly different experiences due to their teachers. One child's third grade teacher had her read one chapter of Charlotte's web as her only differentiated work. When she asked for the chance to learn something new in math she was refused. Two years later, the other child had math grouped by ability and her teacher met privately with her during lunch for a "book club" so that she could study and discuss books that were at a more advanced level. As other students progressed through the year, the book club slowly expanded.
https://www.montgomeryschoolsmd.org/curriculum/specialprograms/admissions/immersion.aspx
The MCPS curriculum was truly awful. Thanks to the negative findings of a recent curriculum audit, it is being gradually being replaced. Hopefully, the new curriculum will be a vast improvement, but I don't know much about it. I would encourage you to check on whether your school is using the new curriculum or the old one. In either case, I would monitor your child's skills and make sure they're learning what you think they should know. Under the old curriculum, there were many areas I felt I needed to supplement at home.
I agree with PPs that if your child can get into a magnet program, instruction and curriculum are vastly improved.
For general purposes, you might find the Hoagies website helpful. It explores all facets of giftedness and different ways to deal with it. They also have a fabulous area of links to enrichment websites for all interests that your kid might enjoy regardless of which school they attend.
https://www.hoagiesgifted.org/
https://www.hoagiesgifted.org/links.htm
Good luck to you and your child as you start the K-12 adventure. While the bad news is that there isn't an easy answer, the good news is that you have several options, all of which you can make successfully work ans that you're not locked-in to anything. I think that having parents who are so concerned and proactive, your child will do great whichever choice you make.