General guidance suggests all gain-based effects – drives, EQ, compression, Wah, filtering – be placed into the amp or before your preamp section, while time-based effects like delay and reverb be placed in the effects loop. Modulation and pitch-shifting requires experimenting with both to see what works best for you, pre or post.
So, how are you primarily using your H9? Mainly for delays and verbs? Use it in the effects loop. The cool thing about H9 is that it can function in “PRE/POST” mode, meaning you can connect I/O 1 to the front of your amp and I/O 2 to your effects loops and designate algorithms to be directed where you want when you need it; using it as a drive? Designate the algorithms as PRE and it will go to the front of the amp. Using it as a delay, designate the algorithm as POST so it will function in the loop. I recommend watching this video: