I have the OAG-L, and use with a ASI174MM which is a larger sensor than yours. I think the plumbing is a bit differet in how it connects so no comment on if you have the exact right pieces. I've been very pleased with the OAG-L, the helical focuser is much smoother than the Celestron (which I also have).
I don't know what's in the filter drawer, but one difference in the Celestron and ZWO is that the Celestron has a rotator built in due to the dovetail connection. The ZWO is screw threads, so the rotation is set by where it gets tight. You may consider adding a rotator. I used this one, which is M54, but they have different sizes:
I was pleasantly surprised at how secure it is, it locks easily, and turns without sag.
One thing to consider is whether you may ever change to a wider format camera. Not sure how relevant it is on a C8 (especially non-edge), but the plumbing with a T connector (I assume that's a 42mm) is pretty small. I'm also unsure whether this is going to add constraint to the room for the prism; it has to extend down into the imaging circle, but stay out of the view of the main sensor along the long edge of the sensor. Someone who has done a 42mm setup may want to comment if there's plenty of room for the prism, I am not sure.
Personally if I were starting up, I might look at doing an M48 or M54 size path from the back of the OTA, just to provide lots of room, and possibly eventually a larger sensor (if the C8 can support it which I do not know). The cost for going M48 or M54 is not much more for the plumbing parts, it's the camera that costs more to go large (and to some extent the filters).
But to your core question: I like the ZWO OAG-L much better than the Celestron OAG. One key reason is so far I have not seen any reflection artifacts on it, as have been reported on the COAG:
ZWO's main drawback is the need for a separate rotator, though the backfocus depth difference leaves plenty of room.
Edited by Linwood, 22 October 2021 - 01:29 PM.