I dont think you should worry too much about a couple of dials, there are other things that will take up alot more memory than dial, like for example if you use a delay that uses S-ram, instead of the SD-ram version.
I am no expert on the details about how much resources they use, I think someone else who know code a lot better than me can answer that for you... Ut a couple of dials...... Dont worry about that
Anyway, I think you should just start patching and if you eventually get to the point where you hit the limit there are always ways to optimize a little bit here and there. But overall I think you should just build what you like and the realise if you actually have issues or not. Use some of the tips above, like use SD-rams for the delay anf you will go far.
About the stereo thing, the essence of stereo is, that its two channels, so if you want stereo....
I know the community library is huge, but its definately worth the while spending some hours looking through it to see whats there. Its a really good way of finding inspiration for your own pacthes. Not only check the community library objects but also the the patches that you find in >
file > library
file > community