All in tank and in inline diffusers are subject to getting dirty or algae covered. So the CO2 flow rate can vary, and it will need cleaning or replacing over time.
IMO, do yourself a favor and just build a reactor. I messed around with other methods for a while, and to me they were a pain to manage. After I built the reactor, I wished I had just quit fooling around and did it from the beginning.
Personally I don't like bubbles in the tank, and my reactor leaves my water crystal clear no bubbles at all.
Besides Griggs, there are also Cerges reactors. That is what I use. Basically a home water filter housing adapted to a reactor. I use a 20" filter housing on my 120G. Brought the unit to the hardware store, and a guy helped me pick out the parts. Once I got the parts home, about 10 minutes to build it.
Research is your friend. Like most things, seems complicated at first, but the more you learn the easier it becomes.
Good luck and look forward to seeing what you come up with.