I would get the tune first. That will give you more noticeable performance and drivability gains as opposed to the slip on or full exhaust. I have Shoodaben’s mountain runner and love it. Much smoother throttle on response and “seat of the pants” performance. After I had the ECU flashed, I swapped out the potato launcher for a Two Brothers Racing Black Series slip on. Much lighter than OEM and much louder. So loud, in fact, I added on of their silencers to tame the noise a bit.
It just depends on what your goals are. If you want to max everything out, you can go a full system with a racing flash, but that gets spendy. For me, I was happy with the overall performance with the slip on and flash. The 2bros is 18” long, and sounded sweet, but I ride with a group of Beemers for long trips. The drone was driving me nuts on long days, so I mellowed out the noise level. If you love loud, I know 2bros has a short “racing” slip on that probably screams.
Basically, what Max said, but Max always brings more intelligence with receipts!