Just so you are aware, macOS Catalina is a full 64-bit OS. Meaning that any software that relies on 32-bit operations will not work in this OS. This generally effects older software such as Office 2011, Adobe CS 6 or the early CC programs/suites to name just a few. There will be others that we think are 64-bit but like those mentioned have parts that rely on old 32-bit drivers/add-ons to work.
There are also a few Hackintosh specific apps that are 32-bit and won't work in Catalina, unless the developer upgrades them to full 64-bit.
With regards your plan to upgrade to Catalina I would state the following:
The use of a second SSD is ideal, as you don't really want Mojave and Catalina on the same drive. While they both run on APFS formatted drives, i.e. from within an APFS container they do not work the same way.
Catalina creates a second volume, it is called 'Catalina Data' on my system. It is created within the APFS Container with the 'Catalina' volume (name I used for my OS drive when installing the beta OS). This 'Data' volume runs any updates, holds any security information etc. The EFI partition is formed outside the APFS Container.
Your existing CLOVER folder will work out of the box with Catalina, mine does with the Beta, so I don't expect yours to be any different. The reason for this is you have created a USBMap.kext, so you have no need to use any USB port limit patches etc.
I'm having trouble with the Gigabyte h370n boards. I have about 10 hackintoshes running 10.14.6 on z370n boards. However, that same build will not boot up on the h370n using identical bios settings and hardware. I'm not sure why. Get stuck at the circle with line through it.