Thanks for the explanation of your goals. With that in mind, here are some various and assorted suggestions (any and all might work).
Best Solution: If you have any kind of budget at all for buying add-ons for ConfigMgr, Do Not Pass Go, Do Not Collect $200, and go straight here: https://patchmypc.com/third-party-patch-management-for-sccm-and-intune . learn about it, grab their demo; justify the cost to whomever holds the budget. If you can afford to get that, once it's setup and running, you'll likely never worry about how to patch Firefox or Chrome again.
Other suggestions:
Yes, doing what you are attempting to do; make collections so you can specifically target applications you create to deploy/update Chrome and Firefox will work. It's just a lot of manual work (by you) to do that. Nothing wrong with that approach. It's just you have to do the collections (and verify they are correct), you have to make the applications (and test they work).
Another "possibility" (if you can't do PatchMyPC, and you potentially want to reduce Collections); but it also means YOU have to do a lot of verification yourself. You "could" not have collections at all. If you design your Google Chrome application (for example), to have a custom Global Condition, where that Global Condition looks for, let's say... "%programFiles%\whatever\chrome.exe must exist", then when you do a Simulated Deployment (for testing your application logic), deployed to "All Servers", and look at Deployment Reports, you'll see that machines that don't have chrome.exe in that folder would report back "Requirements Not Met", so chrome wouldn't install. and then of course your Deployment Type would have the installation for the latest chrome, and the Verification would be the MSI and version of that version of Chrome. (Since you are in the stage of making collections, I'm guessing you already have a working application; but maybe not; sorry if I'm over-explaining something you already know and are rolling your eyes right now)
Personally, I'd try to see if you can get the budget approved for PatchMyPC, and get that working. PatchMyPC isn't only for Firefox/Chrome--they also provide third party patches for many other things as well.
PS: I don't work for them or anything; I just know that currently, they are the best of the breed for 3rd party patching integrated with ECM (there are other vendors, so if you have to do comparisons for your company internal processes, you can look for the other vendors that integrate w/CM for 3rd party patching to compare and contrast)