You probably will be able to use the telescoping stabilizer bar on both.
The bushings are widely available in stores like Tractor Supply that will be suitable for using a Cat II hitch with a Cat I implement. You will need separate bushings for upper and lower links. (Lower link hitch pins Cat I are 7/8”, Cat II are 1-1/8”; upper link pin is 3/4” and 1”)
You will need to replace Pat’s adjustment bolts with a better grade bolt than they furnish as they can’t withstand the stress of heavier attachments, and will bend, and will be difficult to remove to replace afterwards. Tip: Grind the inner bent part of the bolt off before attempting to back the bolt out.
You most likely will need to realign the Pat’s on the lift arms when you re-adjust the lift arms width when you switch from Class I to Class II attachments and vise-versa.
Pat’s says to tighten the adjustment bolts down onto the lift arms, but I don’t know why this is necessary. Seems leaving them loose would provide some swivel that is needed, otherwise the bolts bend when Pat’s “eliminates” the swivel of the ball in the lift arm.