Run your smoker without the elbow first and see how it works. Get a feel for it before you add the elbow. If you’re not happy with it, install the elbow and note any changes or improvements.
In my OKJ Highland, I actually preferred it without the elbow. When I tried using the elbow, I had a hard time getting clean smoke.
As for my mods, I use a charcoal basket, high temp sealant for where the firebox meets the cook chamber. Also gaskets and latches for the doors.
I also have a baffle that I bought off of bbqsmokermods.com. I emailed them when I installed it and they said the elbow wasn’t necessary because of how the baffle was designed for the OKJ.
So definitely give it a test run first. If you’re happy with it, don’t bother installing it.