Glad to hear the firmware flashed. Now that your tablet is restored, your may want to achieve root access. With root, you can permanently remove any bloatware, preinstalled services you don't use, and tweak your kernel parameters to do things like change the default CPU scaling governor, optimize RAM management, change I/O scheduler presets to boost responsiveness, etc.
Because this tablet is Treble supported, there are a number of prebuilt GSI custom ROMs you can install and test. I've only used a LineageOS 19.1 GSI ROM, but it performed quite well. You'll need to read over the tutorials and guides on the official Project Treble forums here on XDA to learn how to install GSI ROMs. You don't need TWRP; everything can be done using fastboot commands. I'll get you a link to the forums.
Project Treble XDA Forums
I'll be doing some how-to guides on GSI ROM installation on the Scepter 8, as well as a guide on optimizing and fully debloating the stock OS. Free time is what I need to get those tasks done, but I am presently too busy with work to contribute much on XDA.