'If I add blue grama to the mix, will I end up with a clumpy looking lawn?'

I'll answer this is a general sense with the caveat that Im about 1500miles to the East of you.

There are 2 types of grass, creepers and clumpers.

Prairie grasses are typically clumpers. Turf grass look of non-clumpy are creepers like Poa 'bluegrass'. This usually occures because of strong rhizomatous growth over time.

Blue grama (or gramma which I prefer cuz it sounds more like how I say grandma) is not a rhizomatous grower. Its quite tufty. But its short growing and can be intermixed.

Froggy

I have some blue grama in lawn that just finished 2nd year. Does't appear to be a problem with clumpy bunches yet. It is a light feathery grass.
Have also seen several places with buffalo grass that does very well also.
Both of these are sold separately and in mixes for lawns.