I have a 5 reel, a 3 reel, and several 2 reel tanks, all Paterson. But I am only comfortable developing 2 tanks at the same time. Since I shoot both 120 & 35mm, the number of reels varies.
Last Saturday I shot 3 rolls of 120 and 4 of 35mm. So it became the 120 in the 5 reel tank, then restart with 2 tanks with 2 35mm reels in each.
I only shoot Neopan 400 but I normally develop the 120 in Rodinal and the 35mm in HC-110. Don't ask why, that just seems to work best for me. But sometimes I will mix 120 and 35mm in the same tank. Then I choose a developer based on what I shot.