Welcome to the forum, Your Grace!
I also struggled with the same thing. I have a 4x6' table at my home and while I love the look of the 36-man French battalions, 24-man units are more practical for my table. I love the look of multi-figure stands and the speed of play is certainly enhanced by them, but I wanted to have flexibility in my collection and be able to maintain the French company structure visually (i.e. keep the pom poms in roughly the right ratio).
I resorted to the Charles Grant method of basing my figures singly. I currently have four 36-man battalions finished. With the extra work of painting a few additional eagle bearers, I can field these models as five battalions of 30, six battalions of 24, or eight battalions of 18 (and any other combination for any rule set I choose to use).
Having said that, even if you build 24-man units, you may detach the grenadiers for some scenarios. A 20-man unit still counts as a 24-man unit, but is slightly more fragile (as should be the case if the packed their grenadiers off) as it only take two casualties to reduce their effectiveness to an 18-man battalion. The combat rules in R2E use groups of six, but fractional groups are rounded up.
Hope that helps!