Biggest difference imho is the wait time between a Form 4 at 12-15 months vs getting a quality Form 1 build done in less than 2-3 including waiting on the parts to come in. Your approval time on a Form 1 once submitted is running around 45-60 days currently. The fact that you have a friend who's a gunsmith is a plus. Gives you access to quality tools and knowledge for a possible Form 1 build. A well thought out Form 1 can rival any of the Form 4 cans for the performance criteria you are looking for.
I don't have any personal experience with the Quietbore kit for 5.56/30 cal BUT a couple of things stand out to me when I've looked at them for Form 1 parts on that configuration. The tube is a 4130 steel w/nitrade coating. It's going to be heavy. It's 9" long. That's pretty long for what you are looking to do. You can accomplish that in a shorter build. The tube is 1.5" and that's the minimum for the calibers you list. A little more volume in the can helps with suppression so I'd consider based upon your list looking at a 1.625" can. They don't give you any information on the baffle size or shape as well as bore size on the tube. They do supply their internals in 3103 SS, but from what I've seen that's an aluminum alloy stainless. Not sure that's appropriate. Are they heat treated? You honestly need at most 2-3 SS "cups" at the beginning to help with erosion, but the balance can be Ti to help with weight. Same concept on the tube, I'd go with Ti from a reputable supplier for weight savings which equals better balance at the end of the rifle.
Here is a list of some additional solvent trap companies you might want to check out.
https://diversifiedmachine.us/shop/
https://maverickprecision.com/produc...g-accessories/
https://superprecisionconcepts.com/
https://www.hawkinnovativetech.com/p.../solvent-trap/
sdtacticalarms.com
Links below should help you TREMENDOUSLY in your research how to build a solvent trap if you go that direction, materials available and what type to choose, as well as minimuim tools necessary to get the job done. You don't have to have a lathe and milling machine to make a good solvent trap. Dremel, some jigs, a file, drill bits and bushings and you can make a VERY nice product. Milling machine and lathe quality cuts, swoops and holes are great, but again not a requirement.
http://form1suppressor.boards.net/
http://www.silencertalk.com/forum/vi...78c8bf8fe814d3
Eform 1 walkthru. Probably one of the best guides I've found.
https://creativearmsllc.com/2019/01/...e-walkthrough/
Let me know if I can help in any way navigate this stuff for you. I've got hundreds of hours of research into this topic. It's addicting!