You can bring in optimized builds, fine, you should worry about the numbers aspect of the game. However, I will say that I am not as generous of a DM as Jack. But, your character should have a strong identity aside from their build. If I have to bring in an example a Soradin perfectly built according to an r/3d6 class guide isn’t going to interest me as much as a build (from r/3d6) reliant upon some goofy mechanic or class fantasy. Honestly sell me on the idea. Especially if narratively the character would fit the bill. I hate class-dips so if you have a multi-class idea that second class better be integral to your character fantasy and not a 2-level dip for a single feature. Coffeelock is an extreme example of what I mean. It’s a build were upon unlocking sorcery points allows one to “bank” the short-rest spell slots as sorcery points, then spending them as spell slots. Therefore, infinite spell slots during a long rest. This is dumb. Do not do this.