I would not alter existing folders. But going forward, I would use the default YYYY/MM folder structure for new images. (This is the one that I use currently. In the past I have used YYYY/MonthName/DD and YYYY/MM/DD. The problem with YYYY/MonthName/DD is that April and August sort first before the other months.) After changing Date Named folder schemes, I tried to correct the old folder. Thais proved to be more troubling for little gain and was not an efficient use of my Lightroom time. Since folders are such a poor organization model for images and Collections are so much more efficient. I only open my folder panel the I need to do some housekeeping like moving older folders to an END and recovering space on my primary drive where performance is greatest and newer images are likely to be the ones that I will access for developing, printing or sharing on the web.
how much would I gain by going with the Subscription to LR
First, your mobile device images would sync directly to the cloud storage and on to the Classic master catalog seamlessly and automatically. The issue in your initial post goes away. If I take a photo on my phone, it automatically gets imported into the Lightroom mobile Phone app, from there to the cloud and back to my master catalog at home. If I cream an "album" on my phone it becomes a Collection on my Master catalog. I can sync proxy files from collections in Classic to the cloud and these show up in Lightroom for the Web and in the Lightroom Mobile app on the phone. This is a convenient way to share photos with friends and family.
Second, if you get a new camera (new since LR6.14 was released), the RAW proprietary format by that camera manufacturer will get correctly demosaic'd by Lightroom and no intermediate DNG conversion is required.
Third, All of the new functionality since LR6.14 is now available and since Adobe added new feature with each new release of LrClassic, you will have these .
Fourth, all of the performance improvements and bug fixes since 6.14 will be available in your upto date version of Lightroom Classic.
Fifth, In Addition to Lightroom Classic, you will get a desktop version of Lightroom Mobile Something that you can use to access your master catalog like you can on the iPhone if you have a laptop and want to take part of the master catalog as you travel. You also get the Photoshop app, 20GB or 1TB of cloud storage. and some other web related Adobe apps.