You'd be well-served to investigate and clarify, for yourself, the technical details of several of the issues you've asked about in your post. First, the 'cloud storage' can be used in multiple ways that are entirely at your discretion. However, the software and particularly the basic 20GB level of cloud storage provided in the basic $10/mth subscription, are not intended for 'storing' your images in the cloud. Rather, this 20GB area is a temporary transfer area to facilitate wireless transfer of images from your mobile LR CC equipment to your long-term desktop LR 'Classic' catalog.

Your LR Classic catalog resides local to your full-function desktop machine, both when using the subscription software as well as your current standalone version. The executable software also installs and resides there locally to your desktop's hardrive.

I can't speak to whether the 32-bit 'installer' software will be / has been broken by Apple. I think I've seen comments that say the installer is not disabled by the new Mac OS. You can wait for that event / need to confirm. Even if Apple did disable new LR6 installs, you don't have to worry about that event until it should occur. At some future point, whether 1-week, 6-months, 2-years, never, only at that point of need will you need to re-evaluate if you want to begin an Adobe subscription. In the meantime, simply assure your LRCAT file, your LR configuration and preset files, and the original image files are regularly and reliably backed-up for disaster recovery and / or transfer to new equipment.

Finally, LRCC and LR Classic are not either / or installations. When you subscribe, you can install and use both, along with PhotoShop. The Classic software is intended for your desktop computer (or full-function laptop) where PS is also installed. The LRCC is intended for your mobile / tablet device for working in the field. That 'temp cloud transfer' area is intended for wireless transfer of preliminary edits from LRCC back to the main Classic catalog. You might share edits between Classic to LRCC, again at most via a 20GB transfer.